mongodb-parameters(5) File Formats Manual mongodb-parameters(5) MONGODB SERVER PARAMETERS SYNOPSIS MongoDB provides a number of configuration options that you can set using: * the setParameter command: db.adminCommand( { setParameter: 1, <parameter>: <value> } ) * the setParameter configuration setting: setParameter: <parameter1>: <value1> ... * the --setParameter command-line option for mongod and mongos: mongod --setParameter <parameter>=<value> mongos --setParameter <parameter>=<value> For additional configuration options, see Configuration File Options, mon- god and mongos. PARAMETERS AUTHENTICATION PARAMETERS authenticationMechanisms Available for both mongod and mongos. Specifies the list of authentication mechanisms the server accepts. Set this to one or more of the following values. If you specify mul- tiple values, use a comma-separated list and no spaces. For descrip- tions of the authentication mechanisms, see Authentication. * * Value * Description * * SCRAM-SHA-1 * RFC 5802 (https://tools.ietf.org/html/rfc5802) standard Salted Challenge Response Authentication Mechanism us- ing the SHA-1 hash function. * * SCRAM-SHA-256 * RFC 7677 (https://tools.ietf.org/html/rfc7677) standard Salted Challenge Response Authentication Mechanism us- ing the SHA-256 hash function. * * MONGODB-X509 * MongoDB TLS/SSL certificate authentication. * * GSSAPI (Kerberos) * External authentication using Kerberos. This mechanism is available only in MongoDB Enterprise (http://www.mongodb.com/products/mongodb-enterprise-ad- vanced?tck=docs_server). * * PLAIN (LDAP SASL) * External authentication using LDAP. You can also use PLAIN for authenticating in-database users. PLAIN transmits passwords in plain text. This mechanism is available only in MongoDB Enterprise (http://www.mon- godb.com/products/mongodb-enterprise-ad- vanced?tck=docs_server). * * MONGODB-OIDC * OpenID Connect is an authentication layer built on top of OAuth2. This mechanism is available only in MongoDB Enterprise (http://www.mongodb.com/products/mongodb-en- terprise-advanced?tck=docs_server). This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to specify both PLAIN and SCRAM-SHA-256 as the authen- tication mechanisms, use the following command: mongod --setParameter authenticationMechanisms=PLAIN,SCRAM-SHA-256 --auth awsSTSRetryCount In previous versions, AWS IAM authentication retried only when the server returned an HTTP 500 error. Available for both mongod and mongos. Type: integer Default: 2 For MongoDB deployments using AWS IAM credentials (https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_ac- cess-keys.html) or AWS IAM environment variables (https://docs.aws.amazon.com/cli/latest/userguide/cli-config- ure-envvars.html#envvars-list). Maximum number of AWS IAM authentication retries after a connection failure. The following example sets awsSTSRetryCount to 15 retries: mongod --setParameter awsSTSRetryCount=15 Alternatively, the following examples uses the setParameter command within mongosh: db.adminCommand( { setParameter: 1, awsSTSRetryCount: 15 } ) clusterAuthMode Available for both mongod and mongos. Set the clusterAuthMode to either sendX509 or x509. Useful during rolling upgrade to use x509 for membership authentication to mini- mize downtime. For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients . This parameter is only available at runtime. To set the parameter, use the setParameter command. db.adminCommand( { setParameter: 1, clusterAuthMode: "sendX509" } ) enableLocalhostAuthBypass Available for both mongod and mongos. Default: true Specify 0 or false to disable localhost authentication bypass. En- abled by default. This parameter is only available at startup. To set the parameter, use the setParameter setting. See Localhost Exception for more information. enforceUserClusterSeparation Available for both mongod and mongos. Set to false to disable the O/OU/DC check when clusterAuthMode is keyFile in your configuration file. This allows clients possessing member certificates to authenticate as users stored in the $external database. The server won't start if clusterAuthMode isn't keyFile in your configuration file. To set the enforceUserClusterSeparation parameter to false, run the following command during startup: mongod --setParameter enforceUserClusterSeparation=false If you set the enforceUserClusterSeparation parameter to false, the server doesn't distinguish between client certificates, which appli- cations use to authenticate, and intra-cluster certificates, which have privileged access. This has no effect if your clusterAuthMode is keyFile. However, if your clusterAuthMode is x509, user certifi- cates that use the allowed scheme are conflated with cluster cer- tificates and granted privileged access. Your existing certificates are granted internal privileges if you do the following: * Create a user, with a name allowed by this parameter. * Set the enforceUserClusterSeparation parameter to false. * Set clusterAuthMode to x509. You must not upgrade from keyFile to x509 without validating that you've removed users with elevated privileges that the enforceUser- ClusterSeparation flag allowed you to create. KeysRotationIntervalSec Default: 7776000 seconds (90 days) Specifies the number of seconds for which an HMAC signing key (https://en.wikipedia.org/wiki/Hash-based_message_authentica- tion_code) is valid before rotating to the next one. This parameter is intended primarily to facilitate authentication testing. This parameter is only available at startup. To set the parameter, use the setParameter setting. ldapForceMultiThreadMode Default: false Enables the performance of concurrent LDAP operations. Only if you are certain that your instance of libldap is safe to use in this mode, enable this flag. You may experience crashes of the MongoDB process if the libldap version you are using is not thread safe. You must use ldapForceMultiThreadMode to use LDAP connection pool. To enable LDAP connection pool, set ldapForceMultiThreadMode and ldapUseConnectionPool to true. If you have any concerns regarding your MongoDB version, OS version or libldap version, please contact MongoDB Support. ldapQueryPassword Available for both mongod and mongos. Type: string The password used to bind to an LDAP server. You must use ldap- QueryUser with this parameter. If not set, mongod or mongos does not attempt to bind to the LDAP server. ldapQueryUser Available for both mongod and mongos. Type: string The user that binds to an LDAP server. You must use ldapQueryPass- word with this parameter. If not set, mongod or mongos does not attempt to bind to the LDAP server. ldapRetryCount Available for both mongod and mongos. Type: integer Default: 0 For MongoDB deployments using LDAP Authorization. Number of operation retries by the server LDAP manager after a net- work error. For example, the following sets ldapRetryCount to 3 seconds: mongod --ldapRetryCount=3 Or, if using the setParameter command within mongosh: db.adminCommand( { setParameter: 1, ldapRetryCount: 3 } ) ldapUserCacheInvalidationInterval Available for mongod only. Starting in MongoDB 5.2, the update interval for cached user infor- mation retrieved from an LDAP server depends on ldapShoul- dRefreshUserCacheEntries: * If true, use ldapUserCacheRefreshInterval. * If false, use ldapUserCacheInvalidationInterval. For use with MongoDB deployments using LDAP Authorization. The interval (in seconds) that the mongod instance waits between ex- ternal user cache flushes. After MongoDB flushes the external user cache, MongoDB reacquires authorization data from the LDAP server the next time an LDAP-authorized user issues an operation. Increasing the value specified increases the amount of time MongoDB and the LDAP server can be out of sync, but reduces the load on the LDAP server. Conversely, decreasing the value specified decreases the time MongoDB and the LDAP server can be out of sync while in- creasing the load on the LDAP server. Defaults to 30 seconds. ldapUserCacheRefreshInterval Available for mongod only. Type: integer Default: 30 seconds Starting in MongoDB 5.2, the update interval for cached user infor- mation retrieved from an LDAP server depends on ldapShoul- dRefreshUserCacheEntries: * If true, use ldapUserCacheRefreshInterval. * If false, use ldapUserCacheInvalidationInterval. For MongoDB deployments using LDAP Authorization. The interval in seconds that mongod waits before refreshing the cached user information from the LDAP server. The maximum interval is 86,400 seconds (24 hours). For example, the following sets ldapUserCacheRefreshInterval to 4000 seconds: mongod --setParameter ldapUserCacheRefreshInterval=4000 Or, if using the setParameter command within mongosh: db.adminCommand( { setParameter: 1, ldapUserCacheRefreshInterval: 4000 } ) ldapUserCacheStalenessInterval Available for mongod only. Type: integer Default: 90 seconds For MongoDB deployments using LDAP Authorization. The interval in seconds that mongod retains the cached LDAP user in- formation after the last cache refresh. If more than ldapUserCacheStalenessInterval seconds elapse without a successful refresh of the user information from the LDAP server, then mongod: * Invalidates the cached LDAP user information. * Is unable to authenticate new sessions for LDAP users until mongod connects to the LDAP server and authorizes the LDAP user. * Authorizes any existing sessions that use previously au- thenticated LDAP users if mongod is unable to connect to the LDAP server. When mongod reconnects to the LDAP server, mongod ensures the LDAP users are correctly authorized. The maximum interval is 86,400 seconds (24 hours). For example, the following sets ldapUserCacheStalenessInterval to 4000 seconds: mongod --setParameter ldapUserCacheStalenessInterval=4000 Or, if using the setParameter command within mongosh: db.adminCommand( { setParameter: 1, ldapUserCacheStalenessInterval: 4000 } ) ldapUseConnectionPool Specifies whether MongoDB should use connection pooling when con- necting to the LDAP server for authentication/authorization. MongoDB uses the following default values: * true on Windows. * true on Linux where MongoDB Enterprise binaries are linked against libldap_r. * false on Linux where MongoDB Enterprise binaries are linked against libldap. You can only set ldapUseConnectionPool during start-up, and cannot change this setting with the setParameter database command. ldapConnectionPoolUseLatencyForHostPriority Default: true A boolean that determines whether the LDAP connection pool (see lda- pUseConnectionPool) should use latency of the LDAP servers to deter- mine the connection order (from lowest latency to highest). You can only set ldapConnectionPoolUseLatencyForHostPriority during start-up, and cannot change this setting during run time with the setParameter database command. ldapConnectionPoolMinimumConnectionsPerHost Default: 1 The minimum number of connections to keep open to each LDAP server. You can only set ldapConnectionPoolMinimumConnectionsPerHost during start-up, and cannot change this setting during run time with the setParameter database command. ldapConnectionPoolMaximumConnectionsPerHost Changed starting in MongoDB versions 5.0.9 and 6.0.0 Changed default value to 2147483647. In previous versions, the default is unset. Default: 2147483647 The maximum number of connections to keep open to each LDAP server. You can only set ldapConnectionPoolMaximumConnectionsPerHost during start-up, and cannot change this setting during run time with the setParameter database command. ldapConnectionPoolMaximumConnectionsInProgressPerHost Changed starting in MongoDB versions 5.0.9 and 6.0.0 Changed default value to 2. In previous versions, the default is unset. Default: 2 The maximum number of in-progress connect operations to each LDAP server. You can only set ldapConnectionPoolMaximumConnectionsInProgressPer- Host during start-up, and cannot change this setting with the setPa- rameter database command. ldapConnectionPoolHostRefreshIntervalMillis Default: 60000 The number of milliseconds in-between health checks of the pooled LDAP connections. You can only set ldapConnectionPoolHostRefreshIntervalMillis during start-up, and cannot change this setting with the setParameter data- base command. ldapConnectionPoolIdleHostTimeoutSecs Default: 300 The maximum number of seconds that the pooled connections to an LDAP server can remain idle before being closed. You can only set ldapConnectionPoolIdleHostTimeoutSecs during start-up, and cannot change this setting with the setParameter data- base command. ldapShouldRefreshUserCacheEntries Available for mongod only. Type: boolean Default: true For MongoDB deployments using LDAP Authorization. Starting in MongoDB 5.2, the update interval for cached user infor- mation retrieved from an LDAP server depends on ldapShoul- dRefreshUserCacheEntries: * If true, use ldapUserCacheRefreshInterval. * If false, use ldapUserCacheInvalidationInterval. You can only set ldapShouldRefreshUserCacheEntries during startup in the configuration file or with the --setParameter option on the com- mand line. For example, the following disables ldapShoul- dRefreshUserCacheEntries: mongod --setParameter ldapShouldRefreshUserCacheEntries=false maxValidateMemoryUsageMB Default: 200 The maximum memory usage limit in megabytes for the validate com- mand. If the limit is exceeded, validate returns as many results as possible and warns that not all corruption might be reported because of the limit. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting oidcIdentityProviders Use this parameter to specify identity provider (IDP) configurations when using OpenID Connect Authentication. oidcIdentityProviders accepts an array of zero or more identity provider (IDP) configurations. An empty array (default) indicates no OpenID Connect support is enabled. When more than one IDP is de- fined, oidcIdentityProviders uses the matchPattern field to select an IDP. Array order determines the priority and the first IDP is al- ways selected. OIDCIDENTITYPROVIDERS FIELDS * * Field * Necessity * Type * Description * * issuer * Required * string * The issuer URI of the IDP that the server should accept tokens from. This must match the iss field in any JWT used for au- thentication. If you specify an unreachable issuer URI, MongoDB: * Logs a warning. * Continues server startup, which allows you to update the issuer URI. * Reattempts issuer contact. If MongoDB reaches the issuer URI and validates the access token, authentication suc- ceeds. If the issuer URI remains unreachable, authenti- cation fails. * * authNamePrefix * Required * string * Unique prefix applied to each generated UserName and RoleName used in authorization. authNamePrefix can only contain the following characters: * alphanumeric characters (combination of a to z and 0 to 9) * hyphens (-) * underscores (_) * * matchPattern * Conditional * string * Regex pattern used to determine which IDP should be used. matchPattern matches against usernames. Array order determines the priority and the first IDP is always selected. matchPattern is required in some configurations, depending on how the user sets supportsHumanFlows: * When only one IdP has supportsHumanFlows set to true (the default), matchPatterns is optional. * When multiple IdP's have supportsHumanFlows set to true (the default), each of these requires matchPatterns. * matchPatterns is optional for any IdP where supportsHu- manFlows is set to false. This is not a security mechanism. matchPattern serves only as an advisory to clients. MongoDB accepts tokens issued by the IDP whose principal names do not match this pattern. * * clientId * Conditional * string * ID provided by the IDP to identify the client that receives the access tokens. Required when supportsHumanFlows is set to true (the default). * * audience * Required * string * Specifies the application or service that the access token is intended for. * * requestScopes * Optional * array[ string ] * Permissions and access levels that MongoDB requests from the IDP. * * principalName * Optional * string * The claim to be extracted from the access token containing MongoDB user identifiers. The default value is sub (stands for subject). * * useAuthorizationClaim * Optional * boolean * Determines if the authorizationClaim is required. The default value is true. If the useAuthorizationClaim field is set to true, the server requires an authorizationClaim for the identity provider's config. This is the default behavior. If the useAuthorizationClaim field is set to false, the autho- rizationClaim field is optional (and ignored if provided). Instead, the server does the following: * Searches the token for a claim whose name is listed in the principalNameClaim field. This is typically named sub. For example: sub: "spencer.jackson@example.com" * Constructs the internal username by concatenating the authNamePrefix, a forward slash (/), and the contents of the claim identified by principalNameClaim within the access token. For example, with a authNamePrefix field value of "mdbinc", the internal username is: mdbinc/spencer.jackson@example.com * Looks for the user with this username and authorizes the client with the roles: { user: "mdbinc/spencer.jackson@example.com", db: "$external" } * * authorizationClaim * Conditional * string * Required, unless useAuthorizationClaim is set to false. Claim extracted from access token that contains MongoDB role names. * * logClaims * Optional * array[ string ] * List of access token claims to include in log and audit mes- sages upon authentication completion. * * JWKSPollSecs * Optional * integer * Frequency, in seconds, to request an updated JSON Web Key Set (JWKS) from the IDP. A setting of 0 disables polling. * * supportsHumanFlows * Optional * bool * Whether the OIDC provider supports human or machine workflows. This affects the clientId and matchPattern fields. You may find it useful to set this field to false with machine workload IdP's to allow them to omit the clientId when it's unneeded. Default: true. This parameter is only available at startup. To set the parameter, use the setParameter setting. ocspEnabled Available on Linux and macOS. Default: true The flag that enables or disables OCSP. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, the following disables OCSP: mongod --setParameter ocspEnabled=false ... Starting in MongoDB 6.0, if ocspEnabled is set to true during ini- tial sync, all nodes must be able to reach the OCSP responder. If a member fails in the STARTUP2 state, set tlsOCSPVerifyTimeout- Secs to a value that is less than 5. * ocspValidationRefreshPeriodSecs * tlsOCSPStaplingTimeoutSecs * tlsOCSPVerifyTimeoutSecs ocspValidationRefreshPeriodSecs Available on Linux. The number of seconds to wait before refreshing the stapled OCSP status response. Specify a number greater than or equal to 1. You can only set ocspValidationRefreshPeriodSecs during startup in the configuration file or with the --setParameter option on the com- mand line. For example, the following sets the parameter to 3600 seconds: mongod --setParameter ocspValidationRefreshPeriodSecs=3600 ... Starting in MongoDB 5.0, the rotateCertificates command and db.ro- tateCertificates() method will also refresh any stapled OCSP re- sponses. * ocspEnabled * tlsOCSPStaplingTimeoutSecs * tlsOCSPVerifyTimeoutSecs opensslCipherConfig Available on Linux only With the use of native TLS/SSL libraries, the parameter opensslCi- pherConfig is supported for Linux/BSD and no longer supported in Windows and macOS. Specify the cipher string for OpenSSL when using TLS/SSL encryption. For a list of cipher strings, see https://www.openssl.org/docs/man1.1.1/man1/ciphers.html (https://www.openssl.org/docs/man1.1.1/man1/ciphers.html). Multiple cipher strings can be provided as a colon-separated list. This parameter is only for use with TLS 1.2 or earlier. To specify cipher suites for use with TLS 1.3, use the opensslCipherSuiteConfig parameter. This parameter is only available at startup. To set the parameter, use the setParameter setting. The use of TLS options is preferred over SSL options. The TLS op- tions have the same functionality as the SSL options. The following example configures a mongod with a opensslCipherConfig cipher string of 'HIGH:!EXPORT:!aNULL@STRENGTH': mongod --setParameter opensslCipherConfig='HIGH:!EXPORT:!aNULL@STRENGTH' --tlsMode requireTLS --tlsCertificateKeyFile Certs/server.pem opensslCipherSuiteConfig Available on Linux only Specify the list of supported cipher suites OpenSSL should permit when using TLS 1.3 encryption. For a list of cipher suites for use with TLS 1.3, see https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set_ci- pher_list.html (https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_set_ci- pher_list.html). Multiple cipher suites can be provided as a colon-separated list. This parameter is only for use with TLS 1.3. To specify cipher strings for use with TLS 1.2 or earlier, use the opensslCipherConfig parameter. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, the following configures a mongod with a opensslCipher- SuiteConfig cipher suite of 'TLS_AES_256_GCM_SHA384' for use with TLS 1.3: mongod --setParameter opensslCipherSuiteConfig='TLS_AES_256_GCM_SHA384' --tlsMode requireTLS --tlsCertificateKeyFile Certs/server.pem opensslDiffieHellmanParameters Available on Linux only Specify the path to the PEM file that contains the OpenSSL Diffie-Hellman parameters when using TLS 1.2 or previous. Specifying the OpenSSL Diffie-Hellman parameters enables support for Ephemeral Diffie-Hellman (DHE) cipher suites during TLS/SSL encryption. This parameter is not supported for use with TLS 1.3. Ephemeral Diffie-Hellman (DHE) cipher suites (and Ephemeral Elliptic Curve Diffie-Hellman (ECDHE) cipher suites) provide Forward Secrecy. Forward Secrecy cipher suites create an ephemeral session key that is protected by the server's private key but never transmitted. This ensures that even if a server's private key is compromised, you can- not decrypt past sessions with the compromised key. If opensslDiffieHellmanParameters is unset but ECDHE is enabled, MongoDB enables DHE using the ffdhe3072 Diffie-Hellman parameter, as defined in RFC-7919#appendix-A.2 (https://tools.ietf.org/html/7919#appendix-A.2). The ffdhe3072 is a strong parameter (specifically, size is greater than 1024). Strong parameters are not supported with Java 6 and 7 unless extended sup- port has been purchased from Oracle. This parameter is only available at startup. To set the parameter, use the setParameter setting. If for performance reasons, you need to disable support for DHE ci- pher suites, use the opensslCipherConfig parameter: mongod --setParameter opensslCipherConfig='HIGH:!EXPORT:!aNULL:!DHE:!kDHE@STRENGTH' ... saslauthdPath Available for both mongod and mongos. Specify the path to the Unix Domain Socket of the saslauthd instance to use for proxy authentication. This parameter is only available at startup. To set the parameter, use the setParameter setting. saslHostName Available for both mongod and mongos. saslHostName overrides MongoDB's default hostname detection for the purpose of configuring SASL and Kerberos authentication. saslHostName does not affect the hostname of the mongod or mongos instance for any purpose beyond the configuration of SASL and Ker- beros. This parameter is only available at startup. To set the parameter, use the setParameter setting. saslHostName supports Kerberos authentication and is only included in MongoDB Enterprise. For more information, see the following: * Linux: Configure MongoDB with Kerberos Authentication on Linux * Windows: Configure MongoDB with Kerberos Authentication on Windows saslServiceName Available for both mongod and mongos. Allows users to override the default Kerberos service name component of the Kerberos principal name, on a per-instance basis. If unspeci- fied, the default value is mongodb. This parameter is only available at startup. To set the parameter, use the setParameter setting. saslServiceName is only available in MongoDB Enterprise. Ensure that your driver supports alternate service names. scramIterationCount Available for both mongod and mongos. Default: 10000 Changes the number of hashing iterations used for all new SCRAM-SHA-1 passwords. More iterations increase the amount of time required for clients to authenticate to MongoDB, but makes passwords less susceptible to brute-force attempts. The default value is ideal for most common use cases and requirements. If you modify this value, it does not change the iteration count for existing passwords. The scramIterationCount value must be 5000 or greater. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following sets the scramIterationCount to 12000. mongod --setParameter scramIterationCount=12000 Or, if using the setParameter command within mongosh: db.adminCommand( { setParameter: 1, scramIterationCount: 12000 } ) * db.changeUserPassword() * db.createUser() * db.updateUser() scramSHA256IterationCount Available for both mongod and mongos. Default: 15000 Changes the number of hashing iterations used for all new SCRAM-SHA-256 passwords. More iterations increase the amount of time required for clients to authenticate to MongoDB, but makes passwords less susceptible to brute-force attempts. The default value is ideal for most common use cases and requirements. If you modify this value, it does not change iteration count for ex- isting passwords. The scramSHA256IterationCount value must be 5000 or greater. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following sets the scramSHA256IterationCount to 20000. mongod --setParameter scramSHA256IterationCount=20000 Or, if using the setParameter command within mongosh: db.adminCommand( { setParameter: 1, scramSHA256IterationCount: 20000 } ) * db.changeUserPassword() * db.createUser() * db.updateUser() sslMode Available for both mongod and mongos. Set the net.ssl.mode to either preferSSL or requireSSL. Useful dur- ing rolling upgrade to TLS/SSL to minimize downtime. For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients . This parameter is only available at runtime. To set the parameter, use the setParameter command. db.adminCommand( { setParameter: 1, sslMode: "preferSSL" } ) tlsMode tlsMode Available for both mongod and mongos. Set to either: * preferTLS * requireTLS The tlsMode parameter is useful during rolling upgrade to TLS/SSL to minimize downtime. This parameter is only available at runtime. To set the parameter, use the setParameter command. db.adminCommand( { setParameter: 1, tlsMode: "preferTLS" } ) For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients . sslMode tlsClusterAuthX509Override Overrides the clusterAuthX509 configuration options. setParameter: tlsClusterAuthX509Override: { attributes: O=MongoDB, OU=MongoDB Server } The parameter supports attributes and extensionValue overrides. When the server authenticates connections from members, it analyzes the X.509 certificate to determine whether it belongs to a cluster member. If the server uses the attributes setting or the attributes field on the tlsClusterAuthX509Override parameter, it checks the Distinguished Name (DN) values of the certificate. If the exten- sionValue setting or the extensionValue field of the tlsCluster- AuthX509Override parameter is set, it checks the extension values of the certificate. If it finds a match, it authorizes the connection as a peer. Use this parameter to rotate certificates when the new certificates have different attributes or extension values. This parameter is only available at startup. To set the parameter, use the setParameter setting. tlsOCSPStaplingTimeoutSecs Available for Linux. The maximum number of seconds the mongod / mongos instance should wait to receive the OCSP status response for its certificates. Specify an integer greater than or equal to (>=) 1. If unset, tlsOC- SPStaplingTimeoutSecs uses the tlsOCSPVerifyTimeoutSecs value. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, the following sets the tlsOCSPStaplingTimeoutSecs to 20 seconds: mongod --setParameter tlsOCSPStaplingTimeoutSecs=20 ... * ocspEnabled * ocspValidationRefreshPeriodSecs * tlsOCSPVerifyTimeoutSecs tlsOCSPVerifyTimeoutSecs Available for Linux and Windows. Default: 5 The maximum number of seconds that the mongod / mongos should wait for the OCSP response when verifying server certificates. Specify an integer greater than or equal to (>=) 1. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, the following sets the tlsOCSPVerifyTimeoutSecs to 20 seconds: mongod --setParameter tlsOCSPVerifyTimeoutSecs=20 ... * ocspEnabled * ocspValidationRefreshPeriodSecs * tlsOCSPStaplingTimeoutSecs tlsUseSystemCA Available for mongod only. Type: boolean Default: false Specifies whether MongoDB loads TLS certificates that are already available to the operating system's certificate authority. When starting a mongod instance with TLS/SSL enabled, you must spec- ify a value for the --tlsCAFile flag, the net.tls.CAFile configura- tion option, or the tlsUseSystemCA parameter. --tlsCAFile, tls.CAFile, and tlsUseSystemCA are all mutually exclu- sive. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set tlsUseSystemCA to true: mongod --setParameter tlsUseSystemCA=true For more information about TLS/SSL and MongoDB, see Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients . tlsWithholdClientCertificate Available for both mongod and mongos. Default: false A TLS certificate is set for a mongod or mongos either by the --tlsClusterFile option or by the --tlsCertificateKeyFile option when --tlsClusterFile is not set. If the TLS certificate is set, by default, the instance sends the certificate when initiating in- tra-cluster communications with other mongod or mongos instances in the deployment. Set tlsWithholdClientCertificate to 1 or true to di- rect the instance to withhold sending its TLS certificate during these communications. Use this option with --tlsAllowConnection- sWithoutCertificates (to allow inbound connections without certifi- cates) on all members of the deployment. tlsWithholdClientCertifi- cate is mutually exclusive with --clusterAuthMode x509. This parameter is only available at startup. To set the parameter, use the setParameter setting. tlsX509ClusterAuthDNOverride Available for both mongod and mongos. An alternative Distinguished Name (DN) that the instance can also use to identify members of the deployment. For a MongoDB deployment that uses x.509 certificates for cluster- AuthMode, deployment members identify each other using x.509 cer- tificates ( net.tls.clusterFile, if specified, and net.tls.certifi- cateKeyFile) during intra-cluster communications. For members of the same deployment, the DN from their certificates must have the same Organization attributes (O's), the Organizational Unit attributes (OU's), and the Domain Components (DC's). If tlsX509ClusterAuthDNOverride is set for a member, the member can also use the override value when comparing the DN components (O's, OU's, and DC's) of the presented certificates. That is the member checks the presented certificates against its net.tls.cluster- File/net.tls.certificateKeyFile. If the DN does not match, the mem- ber checks the presented certificate against the tlsX509Cluster- AuthDNOverride value. If set, you must set this parameter on all members of the deploy- ment. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting You can use this parameter for a rolling update of certificates to new certificates that contain a new DN value. See Rolling Update of x.509 Cluster Certificates that Contain New DN. For more information about membership certificate requirements, see Member Certificate Requirements for details. tlsX509ExpirationWarningThresholdDays Available for both mongod and mongos. Default : 30 mongod / mongos logs a warning on connection if the presented x.509 certificate expires within 30 days of the mongod/mongos system clock. Use the tlsX509ExpirationWarningThresholdDays parameter to control the certificate expiration warning threshold: * Increase the parameter value to trigger warnings farther ahead of the certificate expiration date. * Decrease the parameter value to trigger warnings closer to the certificate expiration date. * Set the parameter to 0 to disable the warning. This parameter has a minimum value of 0. This parameter is only available at startup. To set the parameter, use the setParameter setting. See x.509 Certificates Nearing Expiry Trigger Warnings for more in- formation on x.509 expiration warnings. For more information on x.509 certificate validity, see RFC 5280 4.1.2.5 (https://tools.ietf.org/html/rfc5280#section-4.1.2.5). userCacheInvalidationIntervalSecs Available for mongos only. Default: 30 On a mongos instance, specifies the interval (in seconds) at which the mongos instance checks to determine whether the in-memory cache of user objects has stale data, and if so, clears the cache. If there are no changes to user objects, mongos will not clear the cache. This parameter has a minimum value of 1 second and a maximum value of 86400 seconds (24 hours). This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting authFailedDelayMs Available for both mongod and mongos. Default: 0 Available in MongoDB Enterprise only. The number of milliseconds to wait before informing clients that their authentication attempt has failed. This parameter may be in the range 0 to 5000, inclusive. Setting this parameter makes brute-force login attacks on a database more time-consuming. However, clients waiting for a response from the MongoDB server still consume server resources, and this may ad- versely impact benign login attempts if the server is denying access to many other clients simultaneously. allowRolesFromX509Certificates Available for both mongod and mongos. Default: true A boolean flag that allows or disallows the retrieval of authoriza- tion roles from client x.509 certificates. This parameter is only available at startup. To set the parameter, use the setParameter setting. GENERAL PARAMETERS allowDiskUseByDefault Available for mongod only. Default: True Starting in MongoDB 6.0, pipeline stages that require more than 100 megabytes of memory to execute write temporary files to disk by de- fault. These temporary files last for the duration of the pipeline execution and can influence storage space on your instance. In ear- lier versions of MongoDB, you must pass { allowDiskUse: true } to individual find and aggregate commands to enable this behavior. Individual find and aggregate commands can override the al- lowDiskUseByDefault parameter by either: * Using { allowDiskUse: true } to allow writing temporary files out to disk when allowDiskUseByDefault is set to false * Using { allowDiskUse: false } to prohibit writing temporary files out to disk when allowDiskUseByDefault is set to true This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting mongod --setParameter allowDiskUseByDefault=false allowDiskUseByDefault only works on mongod not mongos. mongos never writes temporary files to disk. Use the setParameter command in a mongosh session that is connected to a running mongod to change the value of the parameter while the server is running: db.adminCommand( { setParameter: 1, allowDiskUseByDefault: false } ) httpVerboseLogging Available for both mongod and mongos. Adds more verbose tracing for curl on Linux and macOS. Has no affect on Windows. By default, the parameter is unset. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting mongos --setParameter httpVerboseLogging=true slowConnectionThresholdMillis Available for both mongod and mongos. Default: 100 Sets the time limit in milliseconds to log the establishment of slow server connections. If a connection takes longer to establish than the slowConnection- ThresholdMillis parameter, an event is added to the log with the message msg field set to "Slow connection establishment". This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets slowConnectionThresholdMillis to 250 mil- liseconds. mongod --setParameter slowConnectionThresholdMillis=250 Or, if using the setParameter command within mongosh: db.adminCommand( { setParameter: 1, slowConnectionThresholdMillis: 250 } ) connPoolMaxConnsPerHost Available for both mongod and mongos. Default: 200 Sets the maximum size of the legacy connection pools for outgoing connections to other mongod instances in the global connection pool. The size of a pool does not prevent the creation of additional con- nections, but does prevent a connection pool from retaining connec- tions in excess of the value of connPoolMaxConnsPerHost. The parameter is separate from the connections in TaskExecutor pools. See ShardingTaskExecutorPoolMaxSize. Only adjust this setting if your driver does not pool connections and you're using authentication in the context of a sharded cluster. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongod --setParameter connPoolMaxConnsPerHost=250 connPoolMaxInUseConnsPerHost Available for both mongod and mongos. Sets the maximum number of in-use connections at any given time for for outgoing connections to other mongod instances in the legacy global connection pool. By default, the parameter is unset. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongod --setParameter connPoolMaxInUseConnsPerHost=100 connPoolMaxConnsPerHost globalConnPoolIdleTimeoutMinutes Available for both mongod and mongos. Sets the time limit that connection in the legacy global connection pool can remain idle before being closed. By default, the parameter is unset. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongos --setParameter globalConnPoolIdleTimeoutMinutes=10 cursorTimeoutMillis Available for both mongod and mongos. Default: 600000 (10 minutes) Sets the expiration threshold in milliseconds for idle cursors be- fore MongoDB removes them; specifically, MongoDB removes cursors that have been idle for the specified cursorTimeoutMillis. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following sets the cursorTimeoutMillis to 300000 milliseconds (5 minutes). mongod --setParameter cursorTimeoutMillis=300000 Or, if using the setParameter command within mongosh: db.adminCommand( { setParameter: 1, cursorTimeoutMillis: 300000 } ) Setting cursorTimeoutMillis to less than or equal to 0 results in all cursors being immediately eligible for timeout. Generally, the timeout value should be greater than the average amount of time for a query to return results. Use tools like the cursor.explain() cur- sor modifier to analyze the average query time and select an appro- priate timeout period. MongoDB cleans up orphaned cursors linked to sessions as part of session management. This means that orphaned cursors with session ids do not use cursorTimeoutMillis to control the timeout. For operations that return a cursor and have an idle period longer than localLogicalSessionTimeoutMinutes, use Mongo.startSession() to perform the operation within an explicit session. To refresh the session, run the refreshSessions command. For details, see Refresh a Cursor with refreshSessions. maxNumActiveUserIndexBuilds Available for mongod only. Type: integer Default: 3 Sets the maximum number of concurrent index builds allowed on the primary. This is a global limit that applies across all collections. Increasing the value of maxNumActiveUserIndexBuilds allows addi- tional concurrent index builds at the cost of increased pressure on the WiredTiger cache. System indexes are not limited to maxNumActiveUserIndexBuilds, how- ever a system index build counts against the limit for user index builds. After the server reaches maxNumActiveUserIndexBuilds, it blocks ad- ditional user index builds until the number of concurrent index builds drops below the maxNumActiveUserIndexBuilds limit. If an in- dex build is blocked, the server logs this message: Too many index builds running simultaneously, waiting until the number of active index builds is below the threshold. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following command sets a limit of 4 concurrent index builds: db.adminCommand( { setParameter: 1, maxNumActiveUserIndexBuilds: 4 } ) See also: * maxIndexBuildMemoryUsageMegabytes * Index Builds on Populated Collections notablescan Available for mongod only. Specify whether all queries must use indexes. If 1, MongoDB will not execute queries that require a collection scan and will return an error. Consider the following example which sets notablescan to 1 or true: db.adminCommand( { setParameter: 1, notablescan: 1 } ) Setting notablescan to 1 can be useful for testing application queries, for example, to identify queries that scan an entire col- lection and cannot use an index. To detect unindexed queries without notablescan, consider reading the Analyze Query Performance and Optimize Query Performance sec- tions and using the logLevel parameter, mongostat and profiling. Don't run production mongod instances with notablescan because pre- venting collection scans can potentially affect queries in all data- bases, including administrative queries. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting notablescan does not allow unbounded queries that use a clustered index because the queries require a full collection scan. For more information, see Collection Scans. ttlMonitorEnabled Available for mongod only. Default: true To support TTL Indexes, mongod instances have a background thread that is responsible for deleting documents from collections with TTL indexes. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting To disable this worker thread for a mongod, set ttlMonitorEnabled to false, as in the following operations: db.adminCommand( { setParameter: 1, ttlMonitorEnabled: false } ) Alternately, you may disable the thread at startup time by starting the mongod instance with the following option: mongod --setParameter ttlMonitorEnabled=false Do not run production mongod instances with ttlMonitorEnabled dis- abled, except under guidance from MongoDB support. Preventing TTL document removal can negatively impact MongoDB internal system oper- ations that depend on TTL Indexes. tcpFastOpenServer Available for both mongod and mongos. Default: true Enables support for accepting inbound TCP Fast Open (TFO) connec- tions to the mongod/mongos from a client. TFO requires both the client and mongod/mongos host machine support and enable TFO: Windows The following Windows operating systems support TFO: * Microsoft Windows Server 2016 and later. * Microsoft Windows 10 Update 1607 and later. macOS macOS 10.11 (El Capitan) and later support TFO. Linux Linux operating systems running Linux Kernel 3.7 or later can support inbound TFO. Set the value of /proc/sys/net/ipv4/tcp_fastopen to enable inbound TFO connections: * Set to 2 to enable only inbound TFO connections. * Set to 3 to enable inbound and outbound TFO connec- tions. This parameter has no effect if the host operating system does not support or is not configured to support TFO connections. This parameter is only available at startup. To set the parameter, use the setParameter setting. See Support for TCP Fast Open for more information on MongoDB TFO support. RFC7413 (https://tools.ietf.org/html/rfc7413). tcpFastOpenClient Available for both mongod and mongos. Default: true Linux Operating System Only Enables support for outbound TCP Fast Open (TFO) connections from the mongod/mongos to a client. TFO requires both the client and the mongod/mongos host machine support and enable TFO. Linux operating systems running Linux Kernel 4.11 or later can sup- port outbound TFO. Set the value of /proc/sys/net/ipv4/tcp_fastopen to enable outbound TFO connections: * 1 to enable only outbound TFO connections. * 3 to enable inbound and outbound TFO connections. This parameter has no effect if the host operating system does not support or is not configured to support TFO connections. This parameter is only available at startup. To set the parameter, use the setParameter setting. See Support for TCP Fast Open for more information on MongoDB TFO support. RFC7413 (https://tools.ietf.org/html/rfc7413). tcpFastOpenQueueSize Available for both mongod and mongos. Default: 1024 As part of establishing a TCP Fast Open (TFO) connection, the client submits a valid TFO cookie to the mongod/mongos before completion of the standard TCP 3-way handshake. The mongod/mongos keeps a queue of all such pending TFO connections. The tcpFastOpenQueueSize parameter sets the size of the queue of pending TFO connections. While the queue is full, the mongod/mongos falls back to the normal three-way handshake for incoming client re- quests and ignores the presence of TFO cookies. Once the queue size falls back below the limit, the mongod/mongos begins accepting new TFO cookies. * Increasing the default queue size may improve the effect of TFO on network performance. However, large queue sizes also increase the risk of server resource exhaustion due to ex- cessive incoming TFO requests. * Decreasing the default queue size may reduce the risk of resource server resource exhaustion due to excessive incom- ing TFO requests. However, small queue sizes may also re- duce the effect of TFO on network performance. The minimum queue size is 0. A queue of 0 effectively dis- ables TFO. This parameter has no effect on host operating systems that do not support or are not configured for TFO connections. See Support for TCP Fast Open for more information on MongoDB TFO support. This parameter is only available at startup. To set the parameter, use the setParameter setting. * RFC7413 TCP Fast Open Section 5: Security Considerations (https://tools.ietf.org/html/rfc7413#section-5) * RFC7413 TCP Fast Open Section 6: TFO Applicability (https://tools.ietf.org/html/rfc7413#section-6) disableJavaScriptJIT Available for mongod only. The MongoDB JavaScript engine uses SpiderMonkey, which implements Just-in-Time (JIT) compilation for improved performance when running scripts. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting To enable the JIT, set disableJavaScriptJIT to false, as in the fol- lowing example: db.adminCommand( { setParameter: 1, disableJavaScriptJIT: false } ) $where will reuse existing JavaScript interpreter contexts, so changes to disableJavaScriptJIT may not take effect immediately for these operations. Alternately, you may enable the JIT at startup time by starting the mongod instance with the following option: mongod --setParameter disableJavaScriptJIT=false indexBuildMinAvailableDiskSpaceMB Available for mongod only. Default: 500 MB Sets the minimum available disk space in megabytes required for in- dex builds. Must be greater than or equal to 0 MB, and less than or equal to 8 TB. 0 disables the minimum disk space requirement. A new index build cannot be started and a current index build is cancelled if the available disk space is below indexBuildMinAvail- ableDiskSpaceMB. If you increase indexBuildMinAvailableDiskSpaceMB, ensure your server has enough available disk space. Also, if you set indexBuild- MinAvailableDiskSpaceMB too high, you might needlessly prevent index builds when there is enough available disk space and indexBuildMi- nAvailableDiskSpaceMB could be set lower. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets indexBuildMinAvailableDiskSpaceMB to 650 MB: db.adminCommand( { setParameter: 1, indexBuildMinAvailableDiskSpaceMB: 650 } ) You can also set indexBuildMinAvailableDiskSpaceMB at startup. For example: mongod --setParameter indexBuildMinAvailableDiskSpaceMB=650 indexMaxNumGeneratedKeysPerDocument Default: 100000 Limits the maximum number of keys generated for a document to pre- vent out of memory errors. It is possible to raise the limit, but if an operation requires more keys than the indexMaxNumGenerated- KeysPerDocument parameter specifies, the operation will fail. This parameter is only available at startup. To set the parameter, use the setParameter setting. maxIndexBuildMemoryUsageMegabytes Default: 200 Limits the amount of memory that simultaneous index builds on one collection may consume for the duration of the builds. The specified amount of memory is shared between all indexes built using a single createIndexes command or its shell helper db.collection.createIn- dexes(). This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The memory consumed by an index build is separate from the WiredTiger cache memory (see cacheSizeGB). maxIndexBuildMemoryUsageMegabytes sets a limit on how much memory the index build uses at once. This can impact performance when the index build process generates and sorts keys for the index. Increas- ing the memory limit improves sorting performance during an index build. Index builds may be initiated either by a user command such as cre- ateIndexes or by an administrative process such as an initial sync. Both are subject to the limit set by maxIndexBuildMemoryUsage- Megabytes. An initial sync populates only one collection at a time and has no risk of exceeding the memory limit. However, it is possible for a user to start index builds on multiple collections in multiple data- bases simultaneously and potentially consume an amount of memory greater than the limit set by maxIndexBuildMemoryUsageMegabytes. To minimize the impact of building an index on replica sets and sharded clusters with replica set shards, use a rolling index build procedure as described on Rolling Index Builds on Replica Sets. Changing maxIndexBuildMemoryUsageMegabytes does not affect an in progress index build if it has already started a collection scan. However, a forced replica set reconfiguration restarts the collec- tion scan and uses the most current maxIndexBuildMemoryUsage- Megabytes provided. * For feature compatibility version (fcv) "4.2" and later, the index build memory limit applies to all index builds. reportOpWriteConcernCountersInServerStatus Default: false A boolean flag that determines whether the db.serverStatus() method and serverStatus command return opWriteConcernCounters information. mongod --setParameter reportOpWriteConcernCountersInServerStatus=true watchdogPeriodSeconds Available for mongod only. Type: integer Default: -1 (disabled) Determines how frequent the Storage Node Watchdog checks the status of the monitored filesystems: * The --dbpath directory * The journal directory inside the --dbpath directory * The directory of --logpath file * The directory of --auditPath file Valid values for watchdogPeriodSeconds are: * -1 (the default), to disable/pause Storage Node Watchdog, or * An integer greater than or equal to 60. * If a filesystem on a monitored directory becomes unrespon- sive, it can take a maximum of nearly twice the value of watchdogPeriodSeconds to terminate the mongod. * If any of its monitored directory is a symlink to other volumes, the Storage Node Watchdog does not monitor the symlink target. For example, if the mongod uses storage.di- rectoryPerDB: true (or --directoryperdb) and symlinks a database directory to another volume, the Storage Node Watchdog does not follow the symlink to monitor the target. To enable Storage Node Watchdog, watchdogPeriodSeconds must be set during startup. mongod --setParameter watchdogPeriodSeconds=60 You can only enable the Storage Node Watchdog at startup. However, once enabled, you can pause the Storage Node Watchdog or change the watchdogPeriodSeconds during run time. Once enabled, * To pause the Storage Node Watchdog during run time, set watchdogPeriodSeconds to -1. db.adminCommand( { setParameter: 1, watchdogPeriodSeconds: -1 } ) * To resume or change the period during run time, set watch- dogPeriodSeconds to a number greater than or equal to 60. db.adminCommand( { setParameter: 1, watchdogPeriodSeconds: 120 } ) It is an error to set watchdogPeriodSeconds at run time if the Stor- age Node Watchdog was not enabled at startup time. tcmallocAggressiveMemoryDecommit To release memory back to the operating system, consider using tc- mallocEnableBackgroundThread instead. Type: integer (0 or 1 only) Default: 0 If you enable tcmallocAggressiveMemoryDecommit, MongoDB: * releases a chunk of memory to system, and * attempts to return all neighboring free chunks. A value of 1 enables tcmallocAggressiveMemoryDecommit; 0 disables this parameter. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting If you enable this parameter, the system will require new memory al- locations for use. Consider enabling tcmallocAggressiveMemoryDecom- mit only on memory-constrained systems and after pursuing other mem- ory and performance options. tcmallocEnableBackgroundThread Type: boolean Default: true If set to true, tcmallocEnableBackgroundThread creates a background thread that periodically releases memory back to the operating sys- tem. The value of tcmallocReleaseRate determines the rate, in bytes per second, at which the background thread releases memory. If tcmallocEnableBackgroundThread is true and tcmallocReleaseRate is 0, MongoDB still releases memory. For improved memory usage, we recommend using the default value of true. To learn more about improvements to performance and memory management, see Upgraded TCMalloc. This parameter is only available at startup. To set the parameter, use the setParameter setting. The following operation sets tcmallocEnableBackgroundThread to false: mongod --setParameter "tcmallocEnableBackgroundThread=false" tcmallocReleaseRate Default: 0 Specifies the tcmalloc release rate (https://github.com/google/tc- malloc/blob/master/docs/tuning.md) in bytes per second. Release rate refers to the rate at which MongoDB releases unused memory to the system. If tcmallocReleaseRate is set to 0 MongoDB doesn't release memory back to the system. Increase this value to return memory faster; decrease it to return memory slower. If tcmallocEnableBackgroundThread is true and tcmallocReleaseRate is 0, MongoDB still releases memory. Starting in MongoDB 8.0, the default value of tcmallocReleaseRate is reduced to 0 due to a tcmalloc upgrade that prioritizes CPU perfor- mance over memory release. Earlier versions of MongoDB used an older version of tcmalloc that set the default tcmallocReleaseRate to 1 to balance memory release and performance. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting To modify the release rate during run time, you can use the setPara- meter command; for example: db.adminCommand( { setParameter: 1, tcmallocReleaseRate: 5.0 } ) You can also set tcmallocReleaseRate at startup time; for example: mongod --setParameter "tcmallocReleaseRate=5.0" fassertOnLockTimeoutForStepUpDown Available for both mongod and mongos. Default: 15 seconds Allows a server that receives a request to step up or step down, to terminate if it is unable to comply (for example due to faulty server disks) within the timeout. This enables a cluster to success- fully elect a new primary node and thus continue to be available. fassertOnLockTimeoutForStepUpDown defaults to 15 seconds. To disable nodes from fasserting, set fassertOnLockTimeoutForStepUpDown=0. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example disables nodes from fasserting: mongod --setParameter fassertOnLockTimeoutForStepUpDown=0 LOGGING PARAMETERS logLevel Available for both mongod and mongos. Specify an integer between 0 and 5 signifying the verbosity of the logging, where 5 is the most verbose. The default logLevel is 0 (Informational). This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets the logLevel to 2: db.adminCommand( { setParameter: 1, logLevel: 2 } ) * logComponentVerbosity * systemLog.verbosity logComponentVerbosity Available for both mongod and mongos. Sets the verbosity levels of various components for log messages. The verbosity level determines the amount of Informational and Debug messages MongoDB outputs. The verbosity level can range from 0 to 5: * 0 is the MongoDB's default log verbosity level, to include Informational messages. * 1 to 5 increases the verbosity level to include Debug mes- sages. For a component, you can also specify -1 to inherit the parent's verbosity level. To specify the verbosity level, use a document similar to the fol- lowing: { verbosity: <int>, <component1>: { verbosity: <int> }, <component2>: { verbosity: <int>, <component3>: { verbosity: <int> } }, ... } For the components, you can specify just the <component>: <int> in the document, unless you are setting both the parent verbosity level and that of the child component(s) as well: { verbosity: <int>, <component1>: <int> , <component2>: { verbosity: <int>, <component3>: <int> } ... } The top-level verbosity field corresponds to systemLog.verbosity which sets the default level for all components. The default value of systemLog.verbosity is 0. The components correspond to the following settings: * accessControl * command * control * ftdc * geo * index * network * query * replication * replication.election * replication.heartbeats * replication.initialSync * replication.rollback * recovery * sharding * storage * storage.journal * transaction * write Unless explicitly set, the component has the verbosity level of its parent. For example, storage is the parent of storage.journal. That is, if you specify a storage verbosity level, this level also ap- plies to: * storage.journal components unless you specify the verbosity level for storage.journal. * storage.recovery components unless you specify the ver- bosity level for storage.recovery. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following sets the default verbosity level to 1, the query to 2, the storage to 2, and the storage.journal to 1. db.adminCommand( { setParameter: 1, logComponentVerbosity: { verbosity: 1, query: { verbosity: 2 }, storage: { verbosity: 2, journal: { verbosity: 1 } } } } ) You can also set parameter logComponentVerbosity at startup time, passing the verbosity level document as a string. mongod --setParameter "logComponentVerbosity={command: 3}" mongosh also provides the db.setLogLevel() to set the log level for a single component. For various ways to set the log verbosity level, see Configure Log Verbosity Levels. maxLogSizeKB Available for both mongod and mongos. Type: non-negative integer Default: 10 Specifies the maximum size, in kilobytes, for an individual at- tribute field in a log entry; attributes exceeding this limit are truncated. Truncated attribute fields print field content up to the maxLog- SizeKB limit and excise field content past that limit, retaining valid JSON formatting. Log entries that contain truncated attributes append a truncated object to the end of the log entry. See log message truncation for more information. A value of 0 disables truncation entirely. Negative values for this parameter are not valid. Using a large value, or disabling truncation with a value of 0, may adversely affect system performance and negatively impact database operations. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets the maximum log line size to 20 kilo- bytes: mongod --setParameter maxLogSizeKB=20 profileOperationResourceConsumptionMetrics Available for mongod only. Type: boolean Default: false Flag that determines whether operations collect resource consumption metrics and report them in the slow query logs. If you enable pro- filing, these metrics are also included. If set to true, running the explain command returns operationMetrics when the verbosity is executionStats or higher. This parameter is only available at startup. To set the parameter, use the setParameter setting. quiet Available for both mongod and mongos. Sets quiet logging mode. If 1, mongod will go into a quiet logging mode which will not log the following events/activities: * connection events; * the drop command, the dropIndexes command, the validate command; and * replication synchronization activities. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting Consider the following example which sets the quiet parameter to 1: db.adminCommand( { setParameter: 1, quiet: 1 } ) systemLog.quiet redactClientLogData Available for both mongod and mongos. Type: boolean Available in MongoDB Enterprise only. Configure the mongod or mongos to redact any message accompanying a given log event before logging. This prevents the program from writing potentially sensitive data stored on the database to the di- agnostic log. Metadata such as error or operation codes, line num- bers, and source file names are still visible in the logs. Use redactClientLogData in conjunction with Encryption at Rest and TLS/SSL (Transport Encryption) to assist compliance with regulatory requirements. To enable log redaction at startup, you can either: * Start mongod with the --redactClientLogData option: mongod --redactClientLogData * Set the security.redactClientLogData option in the configu- ration file: security: redactClientLogData: true ... You can't use the --setParameter option to set redactClientLogData at startup. To enable log redaction on a running mongod or mongos, use the fol- lowing command: db.adminCommand( { setParameter: 1, redactClientLogData : true } ) security.redactClientLogData redactEncryptedFields Available for both mongod and mongos. Type: boolean Default: true Configures mongod and mongos to redact field values of encrypted Bi- nary data from all log messages. * If the redactClientLogData parameter or the secu- rity.redactClientLogData setting is set to false and redac- tEncryptedFields is set to true (the default), encrypted fields are redacted from all log messages. * If the redactClientLogData parameter or security.redact- ClientLogData setting is set to true, all fields are redacted, regardless of the redactEncryptedFields setting. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting traceExceptions Available for both mongod and mongos. Configures mongod to log full source code stack traces for every database and socket C++ exception, for use with debugging. If true, mongod will log full stack traces. This parameter is only available at runtime. To set the parameter, use the setParameter command. Consider the following example which sets the traceExceptions to true: db.adminCommand( { setParameter: 1, traceExceptions: true } ) systemLog.traceAllExceptions suppressNoTLSPeerCertificateWarning Available for both mongod and mongos. Type: boolean Default: false By default, a mongod or mongos with TLS/SSL enabled and net.ssl.al- lowConnectionsWithoutCertificates : true lets clients connect with- out providing a certificate for validation while logging an warning. Set suppressNoTLSPeerCertificateWarning to 1 or true to suppress those warnings. This parameter is only available at startup. To set the parameter, use the setParameter setting. The following operation sets suppressNoTLSPeerCertificateWarning to true: db.adminCommand( { setParameter: 1, suppressNoTLSPeerCertificateWarning: true} ) enableDetailedConnectionHealthMetricLogLines Available for both mongod and mongos. Type: boolean Default: true Determines whether to enable specific log messages related to clus- ter connection health metrics. If enableDetailedConnectionHealth- MetricLogLines is set to false, the following log messages are turned off, but MongoDB still collects data on the cluster connec- tion health metrics: * * Log Message * Description * * Accepted TLS connection from peer * Indicates that the server successfully parsed the peer certificate during the TLS handshake with an accepted ingress connection. * * Ingress TLS handshake complete * Indicates that the TLS handshake with an ingress con- nection is complete. * * Hello completed * Indicates that the initial connection handshake com- pleted on an incoming client connection. MongoDB displays the log message only with the first hello command. * * Auth metrics report * Specifies the completion of a step in the authentica- tion conversation. * * Received first command on ingress connection since ses- sion start or auth handshake * Indicates that an ingress connection received the first command that is not part of the handshake. * * Slow network response send time * Indicates that the time spent, in milliseconds, to send the response back to the client over an ingress connec- tion takes more time than the duration defined by the slowMS server parameter. * * Completed client-side verification of OCSP request * If the peer doesn't include an OCSP (Online Certificate Status Protocol) response to the TLS handshake when an egress TLS connection is established, the server must send an OCSP request to the certificate authority. Mon- goDB writes this log message when the certificate au- thority receives the OCSP response. * * Slow connection establishment * Indicates that the time taken to send a response back to the client over an ingress connection takes longer than the threshold specified with the slowConnection- ThresholdMillis parameter. MongoDB also emits this log message when the connection establishment times out. * * Operation timed out while waiting to acquire connection * Indicates that an operation timed out while waiting to acquire an egress connection. * * Acquired connection for remote operation and completed writing to wire * Indicates that the server took one millisecond or longer to write an outgoing request on an egress con- nection, counting from the instant when the connection establishes. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting DIAGNOSTIC PARAMETERS To facilitate analysis of the MongoDB server behavior by MongoDB engineers, MongoDB logs server statistics to diagnostic files at periodic intervals. For mongod, the diagnostic data files are stored in the diagnostic.data di- rectory under the mongod instance's --dbpath or storage.dbPath. For mongos, the diagnostic data files, by default, are stored in a direc- tory under the mongos instance's --logpath or systemLog.path directory. The diagnostic data directory is computed by truncating the logpath's file ex- tension(s) and concatenating diagnostic.data to the remaining name. For example, if mongos has --logpath /var/log/mongodb/mongos.log.201708015, then the diagnostic data directory is /var/log/mongodb/mongos.diagnos- tic.data/ directory. To specify a different diagnostic data directory for mongos, set the diagnosticDataCollectionDirectoryPath parameter. The following parameters support diagnostic data capture (FTDC): The default values for the diagnostic data capture interval and the maximum sizes are chosen to provide useful data to MongoDB engineers with minimal impact on performance and storage size. Typically, these values will only need modifications as requested by MongoDB engineers for specific diagnos- tic purposes. diagnosticDataCollectionEnabled Available for both mongod and mongos. Type: boolean Default: true Determines whether to enable the collecting and logging of data for diagnostic purposes. Diagnostic logging is enabled by default. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following disables the diagnostic collection: mongod --setParameter diagnosticDataCollectionEnabled=false diagnosticDataCollectionDirectoryPath Available for mongos only. Type: String If Full Time Diagnostic Data Capture (FTDC) is disabled with diag- nosticDataCollectionEnabled or if systemLog.destination is set to syslog, you must restart mongos after setting diagnosticDataCollec- tionDirectoryPath. Specify the directory for the diagnostic directory for mongos. If the directory does not exist, mongos creates the directory. If unspecified, the diagnostic data directory is computed by trun- cating the mongos instance's --logpath or systemLog.path file exten- sion(s) and concatenating diagnostic.data. For example, if mongos has --logpath /var/log/mongodb/mon- gos.log.201708015, then the diagnostic data directory is /var/log/mongodb/mongos.diagnostic.data/. If the mongos cannot create the specified directory, the diagnostic data capture is disabled for that instance. mongos may not be able to create the specified directory if a file with the same name al- ready exists in the path or if the process does not have permissions to create the directory. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting diagnosticDataCollectionDirectorySizeMB Available for both mongod and mongos. Type: integer Default: 200 Specifies the maximum size, in megabytes, of the diagnostic.data di- rectory. If directory size exceeds this number, the oldest diagnos- tic files in the directory are automatically deleted based on the timestamp in the file name. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following sets the maximum size of the directory to 250 megabytes: mongod --setParameter diagnosticDataCollectionDirectorySizeMB=250 The minimum value for diagnosticDataCollectionDirectorySizeMB is 10 megabytes. diagnosticDataCollectionDirectorySizeMB must be greater than maximum diagnostic file size diagnosticDataCollectionFile- SizeMB. diagnosticDataCollectionFileSizeMB Available for both mongod and mongos. Type: integer Default: 10 Specifies the maximum size, in megabytes, of each diagnostic file. If the file exceeds the maximum file size, MongoDB creates a new file. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following sets the maximum size of each diagnostic file to 20 megabytes: mongod --setParameter diagnosticDataCollectionFileSizeMB=20 The minimum value for diagnosticDataCollectionFileSizeMB is 1 megabyte. diagnosticDataCollectionPeriodMillis Available for both mongod and mongos. Type: integer Default: 1000 Specifies the interval, in milliseconds, at which to collect diag- nostic data. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, the following sets the interval to 5000 milliseconds or 5 seconds: mongod --setParameter diagnosticDataCollectionPeriodMillis=5000 The minimum value for diagnosticDataCollectionPeriodMillis is 100 milliseconds. REPLICATION AND CONSISTENCY disableSplitHorizonIPCheck Available for both mongod and mongos. Type: boolean Default: false To configure cluster nodes for split horizon DNS (https://en.wikipedia.org/wiki/Split-horizon_DNS), use host names instead of IP addresses. Starting in MongoDB v5.0, replSetInitiate and replSetReconfig reject configurations that use IP addresses instead of hostnames. Use disableSplitHorizonIPCheck to modify nodes that cannot be up- dated to use host names. The parameter only applies to the configu- ration commands. mongod and mongos do not rely on disableSplitHorizonIPCheck for val- idation at startup. Legacy mongod and mongos instances that use IP addresses instead of host names can start after an upgrade. Instances that are configured with IP addresses log a warning to use host names instead of IP addresses. To allow configuration changes using IP addresses, set disable- SplitHorizonIPCheck=true using the command line: /usr/local/bin/mongod --setParameter disableSplitHorizonIPCheck=true -f /etc/mongod.conf This parameter is only available at startup. To set the parameter, use the setParameter setting. setParameter: disableSplitHorizonIPCheck: true enableOverrideClusterChainingSetting Available for both mongod and mongos. Type: boolean Default: false If enableOverrideClusterChainingSetting is true, replica set sec- ondary members can replicate data from other secondary members even if settings.chainingAllowed is false. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set the enableOverrideClusterChainingSetting for a mongod instance to true: mongod --setParameter enableOverrideClusterChainingSetting=true logicalSessionRefreshMillis Available for both mongod and mongos. Type: integer Default: 300000 (5 minutes) The interval (in milliseconds) at which the cache refreshes its log- ical session records against the main session store. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set the logicalSessionRefreshMillis for a mongod in- stance to 10 minutes: mongod --setParameter logicalSessionRefreshMillis=600000 localLogicalSessionTimeoutMinutes Available for both mongod and mongos. Type: integer Default: 30 This parameter is intended for testing purposes only and not for production use. The time in minutes that a session remains active after its most re- cent use. Sessions that have not received a new read/write operation from the client or been refreshed with refreshSessions within this threshold are cleared from the cache. State associated with an ex- pired session may be cleaned up by the server at any time. This parameter applies only to the instance on which it is set. To set this parameter on replica sets and sharded clusters, you must specify the same value on every member; otherwise, sessions will not function properly. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set the localLogicalSessionTimeoutMinutes for a test mongod instance to 20 minutes: mongod --setParameter localLogicalSessionTimeoutMinutes=20 maxAcceptableLogicalClockDriftSecs Available for both mongod and mongos. Type: integer Default: 31536000 (1 year) The maximum amount by which the current cluster time can be ad- vanced; specifically, maxAcceptableLogicalClockDriftSecs is the max- imum difference between the new value of the cluster time and the current cluster time. Cluster time is a logical time used for order- ing of operations. You cannot advance the cluster time to a new value if the new clus- ter time differs from the current cluster time by more than maxAc- ceptableLogicalClockDriftSecs. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set the maxAcceptableLogicalClockDriftSecs for a mongod instance to 15 minutes: mongod --setParameter maxAcceptableLogicalClockDriftSecs=900 maxSessions Available for both mongod and mongos. Type: integer Default: 1000000 The maximum number of sessions that can be cached. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set the maxSessions for a mongod instance to 1000: mongod --setParameter maxSessions=1000 oplogBatchDelayMillis Available for both mongod and mongos. Type: integer Default: 0 The number of milliseconds to delay applying batches of oplog opera- tions on secondary nodes. By default, oplogBatchDelayMillis is 0, meaning oplog batches are applied with no delay. When there is no delay, MongoDB may apply frequent, small oplog batches to secon- daries. Increasing oplogBatchDelayMillis causes MongoDB to apply oplog batches less frequently on secondaries, with each batch containing larger amounts of data. This reduces IOPS (Input/Output Operations Per Second) on secondaries, but adds latency for writes with write concern "majority". This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, run the following command to set the oplogBatchDe- layMillis for a mongod instance to 20 milliseconds: mongod --setParameter oplogBatchDelayMillis=20 periodicNoopIntervalSecs Available for mongod only. Type: integer Default: 10 The duration in seconds between noop writes on each individual node. This parameter is only available at startup. To set the parameter, use the setParameter setting. To modify this value for a MongoDB Atlas (https://www.mon- godb.com/docs/atlas/) cluster, you must contact Atlas Support (https://www.mongodb.com/docs/atlas/support/). The following example sets the periodicNoopIntervalSecs to 1 second at startup: mongod --setParameter periodicNoopIntervalSecs=1 storeFindAndModifyImagesInSideCollection Available for both mongod and mongos. Type: boolean Default: true Determines whether the temporary documents required for retryable findAndModify commands are stored in the side collection (config.im- age_collection). If storeFindAndModifyImagesInSideCollection is: * true, the temporary documents are stored in the side col- lection. * false, the temporary documents are stored in the replica set oplog. Keep storeFindAndModifyImagesInSideCollection set to true if you: * Have a large retryable findAndModify workload. * Require more temporary document space for retryable find- AndModify commands than is available in the replica set oplog. Secondaries may experience increased CPU usage when storeFindAndMod- ifyImagesInSideCollection is true. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to set storeFindAndModifyImagesInSideCollection to false during startup: mongod --setParameter storeFindAndModifyImagesInSideCollection=false During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, storeFindAndModifyImagesInSideCollection: false } ) TransactionRecordMinimumLifetimeMinutes Available for mongod only. Type: integer Default: 30 The minimum lifetime a transaction record exists in the transactions collection before the record becomes eligible for cleanup. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set the TransactionRecordMinimumLifetimeMinutes for a mongod instance to 20 minutes: mongod --setParameter TransactionRecordMinimumLifetimeMinutes=20 localLogicalSessionTimeoutMinutes enableFlowControl Type: boolean Default: true Enables or disables the mechanism that controls the rate at which the primary applies its writes with the goal of keeping the sec- ondary members' majority committed lag under a configurable maximum value. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For flow control to engage, the replica set/sharded cluster must have: featureCompatibilityVersion (fCV) of 4.2 and read concern ma- jority enabled. That is, enabled flow control has no effect if fCV is not 4.2 or if read concern majority is disabled. flowControlTargetLagSeconds Type: integer Default: 10 The target maximum majority committed lag when running with flow control. When flow control is enabled, the mechanism attempts to keep the majority committed lag under the specified seconds. The pa- rameter has no effect if flow control is disabled. The specified value must be greater than 0. In general, the default settings should suffice; however, if modify- ing from the default value, decreasing, rather than increasing, the value may prove to be more useful. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting flowControlWarnThresholdSeconds Type: integer Default: 10 The amount of time to wait to log a warning once the flow control mechanism detects the majority commit point has not moved. The specified value must be greater than or equal to 0, with 0 to disable warnings. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting initialSyncTransientErrorRetryPeriodSeconds Type: integer Default: 86400 The amount of time in seconds a secondary performing initial sync attempts to resume the process if interrupted by a transient network error. The default value is equivalent to 24 hours. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting initialSyncSourceReadPreference Available for mongod only. Type: String The preferred source for performing initial sync. Specify one of the following read preference modes: * primary * primaryPreferred (Default for voting replica set members) * secondary * secondaryPreferred * nearest (Default for newly added or non-voting replica set members) If the replica set has disabled chaining, the default initialSync- SourceReadPreference read preference mode is primary. You cannot specify a tag set or maxStalenessSeconds to initialSync- SourceReadPreference. If the mongod cannot find a sync source based on the specified read preference, it logs an error and restarts the initial sync process. The mongod exits with an error if it cannot complete the initial sync process after 10 attempts. For more information on sync source selection, see Initial Sync Source Selection. initialSyncSourceReadPreference takes precedence over the replica set's settings.chainingAllowed setting when selecting an initial sync source. After a replica set member successfully completes ini- tial sync, it defers to the value of chainingAllowed when selecting a replication sync source. This parameter is only available at startup. To set the parameter, use the setParameter setting. initialSyncMethod Available for mongod only. Type: String Default: logical Available only in MongoDB Enterprise. Method used for initial sync. Set to logical to use logical initial sync. Set to fileCopyBased to use file copy based initial sync. This parameter only affects the sync method for the member on which it is specified. Setting this parameter on a single replica set mem- ber does not affect the sync method of any other replica set mem- bers. This parameter is only available at startup. To set the parameter, use the setParameter setting. maxNumSyncSourceChangesPerHour Type: integer Default: 3 Sync sources are evaluated each time a sync source is updated and each time a node fetches a batch of oplog entries. If there are more than maxNumSyncSourceChangesPerHour source changes in an hour, the node temporarily stops re-evaluating that sync source. If this para- meter is set with a high value, the node may make unnecessary source changes. This parameter will not prevent a node from starting to sync from another node if it doesn't have a sync source. The node will re-evaluate if a sync source becomes invalid. Similarly, if the pri- mary changes and chaining is disabled, the node will update to sync from the new primary. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting oplogFetcherUsesExhaust Available for mongod only. Type: boolean Default: true Enables or disables streaming replication. Set the value to true to enable streaming replication. Set the value to false to disable streaming replication. If dis- abled, secondaries fetch batches of oplog entries by issuing a re- quest to their sync from source and waiting for a response. This re- quires a network roundtrip for each batch of oplog entries. This parameter is only available at startup. To set the parameter, use the setParameter setting. oplogInitialFindMaxSeconds Available for mongod only. Type: integer Default: 60 Maximum time in seconds for a member of a replica set to wait for the find command to finish during data synchronization. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting replWriterThreadCount Available for mongod only. Type: integer Default: 16 Maximum number of threads to use to apply replicated operations in parallel. Values can range from 1 to 256 inclusive. However, the maximum number of threads used is capped at twice the number of available cores. This parameter is only available at startup. To set the parameter, use the setParameter setting. replWriterMinThreadCount replWriterMinThreadCount Available for mongod only. Type: integer Default: 0 Minimum number of threads to use to apply replicated operations in parallel. Values can range from 0 to 256 inclusive. You can only set replWriterMinThreadCount at startup and cannot change this setting with the setParameter command. Parallel application of replication operations uses up to re- plWriterThreadCount threads. If replWriterMinThreadCount is config- ured with a value less than replWriterThreadCount, the thread pool will timeout idle threads until the total count of threads in the thread pool is equal to replWriterMinThreadCount. replWriterMinThreadCount must be configured with a value that is less than or equal to replWriterThreadCount. This parameter is only available at startup. To set the parameter, use the setParameter setting. rollbackTimeLimitSecs Type: 64-bit integer Default: 86400 (1 day) Maximum age of data that can be rolled back. Negative values for this parameter are not valid. If the time between the end of the to-be-rolledback instance's oplog and the first operation after the common point (the last point where the source node and the to-be-rolledback node had the same data) ex- ceeds this value, the rollback will fail. To effectively have an unlimited rollback period, set the value to 2147483647 which is the maximum value allowed and equivalent to roughly 68 years. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting waitForSecondaryBeforeNoopWriteMS Available for mongod only. Type: integer Default: 10 The length of time (in milliseconds) that a secondary must wait if the afterClusterTime is greater than the last applied time from the oplog. After the waitForSecondaryBeforeNoopWriteMS passes, if the afterClusterTime is still greater than the last applied time, the secondary makes a no-op write to advance the last applied time. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets the waitForSecondaryBeforeNoopWriteMS to 20 milliseconds: mongod --setParameter waitForSecondaryBeforeNoopWriteMS=20 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, waitForSecondaryBeforeNoopWriteMS: 20 } ) createRollbackDataFiles Available for mongod only. Type: boolean Default: true Flag that determines whether MongoDB creates rollback files that contains documents affected during a rollback. By default, createRollbackDataFiles is true and MongoDB creates the rollback files. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets createRollbackDataFiles to false so that the rollback files are not created: mongod --setParameter createRollbackDataFiles=false During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, createRollbackDataFiles: false } ) For more information, see Collect Rollback Data. replBatchLimitBytes Default: 104857600 (100MB) Sets the maximum oplog application batch size in bytes. Values can range from 16777216 (16MB) to 104857600 (100MB) inclu- sive. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets replBatchLimitBytes to 64 MB to limit the oplog application batch size: mongod --setParameter replBatchLimitBytes=67108864 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, replBatchLimitBytes: 64 * 1024 * 1024 } ) mirrorReads Available for mongod only. Type: Document Default: { samplingRate: 0.01, maxTimeMS: 1000 } Specifies the settings for mirrored reads for the mongod instance. The settings only take effect when the member is a primary. The parameter mirrorReads takes a JSON document with the following fields: * * Field * Description * * samplingRate * The sampling rate used to mirror a subset of operations that support mirroring to a subset of electable (specifically, priority greater than 0) secondaries. That is, the primary mirrors reads to each electable secondary at the specified sampling rate. Valid values are: * * 0.0 * Turns off mirroring. * * 1.0 * The primary mirrors all operations that supports mirroring to each electable sec- ondary. * * Number between 0.0 and 1.0 (exclusive) * The primary randomly samples each elec- table secondary at the specified rate to be sent mirrored reads. For example, given a replica set with a primary and two electable secondaries and a sampling rate of 0.10, the primary mirrors reads to each electable secondary at the sampling rate of 10 percent such that one read may be mirrored to one secondary and not to the other or to both or to neither. That is, if the primary receives 100 operations that can be mirrored, the sampling rate of 0.10 may result in 8 reads being mirrored to one secondary and 13 reads to the other or 10 to each, etc. The default value is 0.01. * * maxTimeMS * The maximum time in milliseconds for the mirrored reads. The default value is 1000. The maxTimeMS for the mirrored reads is separate from the maxTimeMS of the original read being mirrored. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting If you specify from the configuration file or on the command line, enclose the mirrorReads document in quotes. For example, the following sets the mirror reads sampling rate to 0.10 from the command line: mongod --setParameter mirrorReads='{ samplingRate: 0.10 }' Or, to specify in a configuration file: setParameter: mirrorReads: '{samplingRate: 0.10}' Or if using the setParameter command in a mongosh session that is connected to a running mongod, do not enclose the document in quotes: db.adminCommand( { setParameter: 1, mirrorReads: { samplingRate: 0.10 } } ) allowMultipleArbiters Available for mongod only. Type: boolean Default: false Specifies whether the replica set allows the use of multiple ar- biters. The use of multiple arbiters is not recommended: * Multiple arbiters prevent the reliable use of the majority write concern. MongoDB counts arbiters in calculating a membership majority, but arbiters do not store data. With the inclusion of multiple arbiters, it's possible for a ma- jority write operation to return success before the write replicates to a majority of data bearing nodes. * Multiple arbiters allow replica sets to accept writes even when the replica set doesn't have sufficient secondaries for data replication. For more information, see Concerns with Multiple Arbiters. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongod --setParameter allowMultipleArbiters=true SHARDING PARAMETERS analyzeShardKeyCharacteristicsDefaultSampleSize Available for mongod only. Type: integer Default: 10000000 If sampleRate and sampleSize are not set when you run analyzeShard- Key, specifies the number of documents to sample when calculating shard key characteristics metrics. Must be greater than 0. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets analyzeShardKeyCharacteristicsDefaultSampleSize to 10000 at startup: mongod --setParameter analyzeShardKeyCharacteristicsDefaultSampleSize=10000 During run time, you can set or modify the parameter with the setPa- rameter command: db.adminCommand( { setParameter: 1, analyzeShardKeyCharacteristicsDefaultSampleSize: 10000 } ) analyzeShardKeyNumMostCommonValues Available for mongod only. Type: integer Default: 5 Specifies the number of most common shard key values to return. If the collection contains fewer unique shard keys than this value, an- alyzeShardKeyNumMostCommonValues returns that number of most common values. Must be greater than 0 and less than or equal to 1000. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets analyzeShardKeyNumMostCommonValues to 3 at startup: mongod --setParameter analyzeShardKeyNumMostCommonValues=3 During run time, you can set or modify the parameter with the setPa- rameter command: db.adminCommand( { setParameter: 1, analyzeShardKeyNumMostCommonValues: 3 } ) analyzeShardKeyNumRanges Available for mongod only. Type: integer Default: 100 Specifies the number of ranges to partition the shard key space into when calculating the hotness of shard key ranges. Must be greater than 0 and less than or equal to 10000. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets analyzeShardKeyNumRanges to 50 at startup: mongod --setParameter analyzeShardKeyNumRanges=50 During run time, you can set or modify the parameter with the setPa- rameter command: db.adminCommand( { setParameter: 1, analyzeShardKeyNumRanges: 50 } ) analyzeShardKeyMonotonicityCorrelationCoefficientThreshold Available for mongod only. Type: double Default: 0.7 Specifies the RecordId correlation coefficient threshold used to de- termine if a shard key is monotonically changing in insertion order. Must be greater than 0 and less than or equal to 1. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets analyzeShardKeyMonotonicityCorrelationCoefficient- Threshold to 1 at startup: mongod --setParameter analyzeShardKeyMonotonicityCorrelationCoefficientThreshold=1 During run time, you can set or modify the parameter with the setPa- rameter command: db.adminCommand( { setParameter: 1, analyzeShardKeyMonotonicityCorrelationCoefficientThreshold: 1 } ) autoMergerIntervalSecs Available for mongod only. Type: integer Default: 3600 When AutoMerger is enabled, specifies the amount of time between au- tomerging rounds, in seconds. The default value is 3600 seconds, or one hour. autoMergerIntervalSecs can only be set on config servers. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets autoMergerIntervalSecs to 7200 seconds, or two hours, at startup: mongod --setParameter autoMergerIntervalSecs=7200 During run time, you can set or modify the parameter with the setPa- rameter command: db.adminCommand( { setParameter: 1, autoMergerIntervalSecs: 7200 } ) autoMergerThrottlingMS Available for mongod only. Type: integer Default: 15000 When AutoMerger is enabled, specifies the minimum amount time be- tween merges initiated by the AutoMerger on the same collection, in milliseconds. autoMergerThrottlingMS can only be set on config servers. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets autoMergerThrottlingMS to 60000 milliseconds, or one minute, at startup: mongod --setParameter autoMergerThrottlingMS=60000 During run time, you can set or modify the parameter with the setPa- rameter command: db.adminCommand( { setParameter: 1, autoMergerThrottlingMS: 60000 } ) balancerMigrationsThrottlingMs Available for mongod only. Type: integer Default: 1000 Specifies the minimum amount of time between two consecutive balanc- ing rounds. This allows you to throttle the balancing rate. This pa- rameter only takes effect on config server nodes. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets balancerMigrationsThrottlingMs to 2000 millisec- onds at startup: mongod --setParameter balancerMigrationsThrottlingMs=2000 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, balancerMigrationsThrottlingMs: 2000 } ) chunkDefragmentationThrottlingMS Available for both mongod and mongos. Type: integer Default: 0 Specifies the minimum time period (in milliseconds) between consecu- tive split and merge commands run by the balancer when the chunks in a sharded collection are defragmented. chunkDefragmentationThrot- tlingMS limits the rate of split and merge commands. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets chunkDefragmentationThrottlingMS to 10 milliseconds: mongod --setParameter chunkDefragmentationThrottlingMS=10 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, chunkDefragmentationThrottlingMS: 10 } ) chunkMigrationConcurrency Available starting in MongoDB 7.0, 6.3, 6.0.6 (and 5.0.15). Available for mongod only. Type: integer Default: 1 Specifies an integer that sets the number of threads on the source shard and the receiving shard for chunk migration. Chunk migrations use the number of threads that you set on the receiving shard for both the source and receiving shard. Increasing the concurrency improves chunk migration performance, but also increases the workload and disk IOPS usage on the source shard and the receiving shard. Maximum value is 500. You should typically use half the total number of CPU cores as threads. For example, if the total is 16 cores, set chunkMigra- tionConcurrency to 8 threads (or fewer). If chunkMigrationConcurrency is greater than 1, the _secondaryThrot- tle configuration setting is ignored. The _secondaryThrottle setting determines when the chunk migration proceeds with the next document in the chunk. For details, see Range Migration and Replication. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets chunkMigrationConcurrency to 5: mongod --setParameter chunkMigrationConcurrency=5 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, chunkMigrationConcurrency: 5 } ) To configure collection balancing, see configureCollectionBalancing. To learn about defragmenting sharded collections, see Defragment Sharded Collections. disableResumableRangeDeleter Available for mongod only. Type: boolean Default: false If set on a shard's primary, specifies if range deletion is paused on the shard. If set to true, cleanup of ranges containing orphaned documents is paused. The shard can continue to donate chunks to other shards, but the donated documents will not be removed from this shard until you set this parameter to false. This shard can continue to receive chunks from other shards as long as it does not have a pending range deletion task in the config.rangeDeletions col- lection that overlaps with the incoming chunk's range. When disableResumableRangeDeleter is true, chunk migrations fail if orphaned documents exist on the recipient shard's primary in the same range as the incoming chunks. The parameter has no effect on the mongod if it is not the shard's primary. If you set disableResumableRangeDeleter parameter to true, ensure that you apply it consistently for all members in the shard's replica set. In the event of a failover, this setting's value on the new primary dictates the behavior of the range deleter. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongod --setParameter disableResumableRangeDeleter=false enableShardedIndexConsistencyCheck Available for mongod only. Type: boolean Default: true If set on the config server's primary, enables or disables the index consistency check for sharded collections. The parameter has no ef- fect on the mongod if it is not the config server's primary. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets enableShardedIndexConsistencyCheck to false for a config server primary: mongod --setParameter enableShardedIndexConsistencyCheck=false During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, enableShardedIndexConsistencyCheck: false } ) * shardedIndexConsistencyCheckIntervalMS parameter * shardedIndexConsistency metrics returned by the serverSta- tus command. opportunisticSecondaryTargeting Available for mongos only. Type: boolean Default: false Determines whether mongos performs opportunistic reads against replica sets. When this parameter is set to true, mongos directs secondary reads to secondaries with active connections. It sends the request to the first secondary that accepts the connection. When this parameter is set to false, mongos holds secondary reads until it can establish a connection to a specific secondary, (except in the case of hedged reads). Under certain workloads, opportunistic reads may trigger the opening of unnecessary connections from mongos to mongod and reduce overall performance. This parameter should not be enabled unless your ap- plication has a specific need for the feature. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to set opportunisticSecondaryTargeting during startup: mongos --setParameter opportunisticSecondaryTargeting=true shardedIndexConsistencyCheckIntervalMS Available for mongod only. Type: integer Default: 600000 If set on the config server's primary, the interval, in millisec- onds, at which the config server's primary checks the index consis- tency of sharded collections. The parameter has no effect on the mongod if it is not the config server's primary. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, the following sets the interval at 300000 milliseconds (5 minutes) at startup: mongod --setParameter shardedIndexConsistencyCheckIntervalMS=300000 * enableShardedIndexConsistencyCheck parameter * shardedIndexConsistency metrics returned by the serverSta- tus commandq enableFinerGrainedCatalogCacheRefresh Available for both mongod and mongos. Type: boolean Default: true This parameter allows the catalog cache to be refreshed only if the shard needs to be refreshed. If disabled, any stale chunk will cause the entire chunk distribution for a collection to be considered stale and force all routers who contact the shard to refresh their shard catalog cache. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongod --setParameter enableFinerGrainedCatalogCacheRefresh=true mongos --setParameter enableFinerGrainedCatalogCacheRefresh=true * Sharding * shardingStatistics.catalogCache maxTimeMSForHedgedReads Starting in MongoDB 8.0, hedged reads are deprecated. Queries that specify the read preference nearest no longer use hedged reads by default. If you explicitly specify a hedged read, MongoDB performs a hedged read and logs a warning. Available for mongos only. Type: integer Default: 150 Specifies the maximum time limit (in milliseconds) for the hedged read. That is, the additional read sent to hedge the read operation uses the maxTimeMS value of maxTimeMSForHedgedReads while the read operation that is being hedged uses the maxTimeMS value specified for the operation. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to set the limit to 200 milliseconds, you can issue the following during startup: mongos --setParameter maxTimeMSForHedgedReads=200 Or if using the setParameter command in a mongosh session that is connected to a running mongos: db.adminCommand( { setParameter: 1, maxTimeMSForHedgedReads: 200 } ) * readHedgingMode * Hedged Reads maxCatchUpPercentageBeforeBlockingWrites Available for mongod only. Type: integer Default: 10 For moveChunk and moveRange operations, specifies the maximum per- centage of untrasferred data allowed by the migration protocol (ex- pressed in percentage of the total chunk size) to transition from the catchup phase to the commit phase. Setting a higher catchup percentage can decrease the amount of time it takes for the migration to complete at the cost of increased la- tency during concurrent upsert and delete operations. This parameter is only available at startup. To set the parameter, use the setParameter setting. Starting in MongoDB 7.1 (and 7.0.1), you can set the parameter dur- ing runtime. For example, to set the maximum percentage to 20, you can issue the following during startup: mongod --setParameter maxCatchUpPercentageBeforeBlockingWrites=20 Starting in MongoDB 7.1 (and 7.0.1), you can set the parameter dur- ing runtime with the setParameter command: db.adminCommand( { setParameter: 1, maxCatchUpPercentageBeforeBlockingWrites: 20} ) Live Migration Protocol (https://github.com/mongodb/mongo/blob/mas- ter/src/mongo/db/s/README.md#the-live-migration-protocol) metadataRefreshInTransactionMaxWaitBehindCritSecMS Available for mongod only. Type: integer Default: 500 Limits the time a shard waits for a critical section within a trans- action. When a query accesses a shard, a chunk migration or DDL operation may already hold the critical section for the collection. If the query finds the critical section is taken, the shard waits until the critical section has been released. When the shard returns control to mongos, mongos retries the query. However, if a multi-shard transaction interacts with an operation that takes the critical sec- tion on multiple shards, the interaction can result in a distributed deadlock. metadataRefreshInTransactionMaxWaitBehindCritSecMS limits the maxi- mum time a shard waits within a transaction for the critical section to be released. To reduce the maximum wait time for the critical section within a transaction, lower the value of metadataRefreshInTransactionMaxWait- BehindCritSecMS. If metadataRefreshInTransactionMaxWaitBehindCritSecMS is too low, mongos could use all of its retry attempts and return an error. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to set metadataRefreshInTransactionMaxWaitBehindCrit- SecMS to 400 milliseconds: db.adminCommand( { setParameter: 1, metadataRefreshInTransactionMaxWaitBehindCritSecMS: 400 } ) queryAnalysisSamplerConfigurationRefreshSecs Available for both mongod and mongos. Type: integer Default: 10 Interval that a sampler (mongos or mongod) refreshes its query ana- lyzer sample rates. The sample rate configured by the configureQueryAnalyzer command is divided among mongos instances in the sharded cluster or mongod in- stances in the replica set based on the traffic going through them. To make the sample rate assignment for a mongos or mongod more re- sponsive to the traffic going through it, decrease this value. We recommend using the default value. This parameter is only available at startup. To set the parameter, use the setParameter setting. Starting in MongoDB 7.0.1, you can set queryAnalysisSamplerConfigu- rationRefreshSecs during run time. This example sets queryAnalysisSamplerConfigurationRefreshSecs to 60 seconds at startup on a mongod instance: mongod --setParameter queryAnalysisSamplerConfigurationRefreshSecs=60 This example sets queryAnalysisSamplerConfigurationRefreshSecs to 60 seconds at startup on a mongos instance: mongos --setParameter queryAnalysisSamplerConfigurationRefreshSecs=60 To set the value to 30 seconds, run the following: db.adminCommand( { setParameter: 1, queryAnalysisSamplerConfigurationRefreshSecs: 30 } ) queryAnalysisWriterIntervalSecs Available for mongod only. Type: integer Default: 90 Interval that sampled queries are written to disk, in seconds. This parameter is only available at startup. To set the parameter, use the setParameter setting. Starting in MongoDB 7.0.1, you can set queryAnalysisWriterInter- valSecs during run time. This example sets queryAnalysisWriterIntervalSecs to 60 seconds at startup on a mongod instance: mongod --setParameter queryAnalysisWriterIntervalSecs=60 To set the value to 60 seconds, run the following: db.adminCommand( { setParameter: 1, queryAnalysisWriterIntervalSecs: 60 } ) queryAnalysisWriterMaxMemoryUsageBytes Available for mongod only. Type: integer Default: 100 * 1024 * 1024 Maximum amount of memory in bytes that the query sampling writer is allowed to use. Once the limit is reached, all new queries and diffs are discarded from sampling until the buffer is flushed. Must be greater than 0. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets queryAnalysisWriterMaxMemoryUsageBytes to 10000000 at startup on a mongod instance: mongod --setParameter queryAnalysisWriterMaxMemoryUsageBytes=10000000 queryAnalysisWriterMaxBatchSize Available for mongod only. Type: integer Default: 100000 Maximum number of sampled queries to write to disk at once. Must be greater than 0 and less than or equal to 100000. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets queryAnalysisWriterMaxBatchSize to 1000 at startup on a mongod instance: mongod --setParameter queryAnalysisWriterMaxBatchSize=1000 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, queryAnalysisWriterMaxBatchSize: 1000 } ) queryAnalysisSampleExpirationSecs Available for mongod only. Type: integer Default: 7 * 24 * 3600 Amount of time that a sampled query document exists before being re- moved by the TTL monitor, in seconds. Must be greater than 0. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting This example sets queryAnalysisSampleExpirationSecs to 691200 (8 * 24 * 3600) at startup on a mongod instance: mongod --setParameter queryAnalysisSampleExpirationSecs=691200 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, queryAnalysisSampleExpirationSecs: 691200 } ) readHedgingMode Available for mongos only. Type: string Default: on Specifies whether mongos supports hedged reads for those read opera- tions whose read preference have enabled the hedged read option. Available values are: * * Value * Description * * on * The mongos instance supports hedged reads for read op- erations whose read preference have enabled the hedged read option. * * off * The mongos instance does not support hedged reads. That is, hedged reads are unavailable, even for read opera- tions whose read preference have enabled the hedged read option. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to turn off hedged read support for a mongos instance, you can issue the following during startup: mongos --setParameter readHedgingMode=off Or if using the setParameter command in a mongosh session that is connected to a running mongos: db.adminCommand( { setParameter: 1, readHedgingMode: "off" } ) * Hedged Reads * maxTimeMSForHedgedReads routingTableCacheChunkBucketSize Available for both mongod and mongos. Type: integer Default: 500 Specifies the size of the routing table cache buckets used to imple- ment chunk grouping optimization. Must be greater than 0. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, to set the cache chunk bucket size to 250 on a mongod, issue the following command at startup: mongod --setParameter routingTableCacheChunkBucketSize=250 shutdownTimeoutMillisForSignaledShutdown Available for mongod only. Type: integer Default: 15000 Specifies the time (in milliseconds) to wait for any ongoing data- base operations to complete before initiating a shutdown of mongod in response to a SIGTERM signal. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to set the time to 250 milliseconds, you can issue the following during startup: mongod --setParameter shutdownTimeoutMillisForSignaledShutdown=250 Or if using the setParameter command in a mongosh session that is connected to a running mongod: db.adminCommand( { setParameter: 1, shutdownTimeoutMillisForSignaledShutdown: 250 } ) mongosShutdownTimeoutMillisForSignaledShutdown Available for mongos only. Type: integer Default: 15000 Specifies the time (in milliseconds) to wait for any ongoing data- base operations to complete before initiating a shutdown of mongos in response to a SIGTERM signal. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to set the time to 250 milliseconds, you can issue the following during startup: mongos --setParameter mongosShutdownTimeoutMillisForSignaledShutdown=250 Or if using the setParameter command in a mongosh session that is connected to a running mongos: db.adminCommand( { setParameter: 1, mongosShutdownTimeoutMillisForSignaledShutdown: 250 } ) ShardingTaskExecutorPoolHostTimeoutMS Available for both mongod and mongos. Type: integer Default: 300000 (5 minutes) Maximum time that mongos goes without communication to a host before mongos drops all connections to the host. If set, ShardingTaskExecutorPoolHostTimeoutMS should be greater than the sum of ShardingTaskExecutorPoolRefreshRequirementMS and Shard- ingTaskExecutorPoolRefreshTimeoutMS. Otherwise, mongos adjusts the value of ShardingTaskExecutorPoolHostTimeoutMS to be greater than the sum. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets ShardingTaskExecutorPoolHostTimeoutMS to 120000 during startup: mongos --setParameter ShardingTaskExecutorPoolHostTimeoutMS=120000 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolHostTimeoutMS: 120000 } ) ShardingTaskExecutorPoolMaxConnecting Available for both mongod and mongos. Type: integer Default: 2 Maximum number of simultaneous initiating connections (including pending connections in setup/refresh state) each TaskExecutor con- nection pool can have to a mongod instance. You can set this parame- ter to control the rate at which mongos adds connections to a mongod instance. If set, ShardingTaskExecutorPoolMaxConnecting should be less than or equal to ShardingTaskExecutorPoolMaxSize. If it is greater, mongos ignores the ShardingTaskExecutorPoolMaxConnecting value. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets ShardingTaskExecutorPoolMaxConnecting to 20 during startup: mongos --setParameter ShardingTaskExecutorPoolMaxConnecting=20 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMaxConnecting: 20 } ) ShardingTaskExecutorPoolMaxSize Available for both mongod and mongos. Type: integer Default: 2 64 - 1 Maximum number of outbound connections each TaskExecutor connection pool can open to any given mongod instance. The maximum possible connections to any given host across all TaskExecutor pools is: ShardingTaskExecutorPoolMaxSize * taskExecutorPoolSize This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets ShardingTaskExecutorPoolMaxSize to 20 during startup: mongos --setParameter ShardingTaskExecutorPoolMaxSize=20 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMaxSize: 20 } ) mongos can have up to n TaskExecutor connection pools, where n is the number of cores. See taskExecutorPoolSize. ShardingTaskExecutorPoolMinSize ShardingTaskExecutorPoolMaxSizeForConfigServers Available for both mongod and mongos. Type: integer Default: -1 Optional override for ShardingTaskExecutorPoolMaxSize to set the maximum number of outbound connections each TaskExecutor connection pool can open to a configuration server. When set to: * -1, ShardingTaskExecutorPoolMaxSize is used. This is the default. * an integer value greater than -1, overrides the maximum number of outbound connections each TaskExecutor connection pool can open to a configuration server. Parameter only applies to sharded deployments. The following example sets ShardingTaskExecutorPoolMaxSize to 2 dur- ing startup, which sets the maximum number of outbound connections each TaskExecutor connection pool can open to a configuration server to 2: This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting mongos --setParameter ShardingTaskExecutorPoolMaxSizeForConfigServers=2 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMaxSizeForConfigServers: 2 } ) ShardingTaskExecutorPoolMinSize Available for both mongod and mongos. Type: integer Default: 1 Minimum number of outbound connections each TaskExecutor connection pool can open to any given mongod instance. ShardingTaskExecutorPoolMinSize connections are created the first time a connection to a new host is requested from the pool. While the pool is idle, the pool maintains this number of connections un- til ShardingTaskExecutorPoolHostTimeoutMS milliseconds pass without any application using that pool. For a mongos using the warmMinConnectionsInShardingTaskExecutor- PoolOnStartup parameter, the ShardingTaskExecutorPoolMinSize parame- ter also controls how many connections to each shard host are estab- lished on startup of the mongos instance before it begins accepting incoming client connections. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets ShardingTaskExecutorPoolMinSize to 2 dur- ing startup: mongos --setParameter ShardingTaskExecutorPoolMinSize=2 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMinSize: 2 } ) mongos can have up to n TaskExecutor connection pools, where n is the number of cores. See taskExecutorPoolSize. * ShardingTaskExecutorPoolMaxSize * warmMinConnectionsInShardingTaskExecutorPoolOnStartup ShardingTaskExecutorPoolMinSizeForConfigServers Available for both mongod and mongos. Type: integer Default: -1 Optional override for ShardingTaskExecutorPoolMinSize to set the minimum number of outbound connections each TaskExecutor connection pool can open to a configuration server. When set to: * -1, ShardingTaskExecutorPoolMinSize is used. This is the default. * an integer value greater than -1, overrides the minimum number of outbound connections each TaskExecutor connection pool can open to a configuration server. Parameter only applies to sharded deployments. The following example sets ShardingTaskExecutorPoolMinSize to 2 dur- ing startup, which sets the minimum number of outbound connections each TaskExecutor connection pool can open to a configuration server to 2: This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting mongos --setParameter ShardingTaskExecutorPoolMinSizeForConfigServers=2 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolMinSizeForConfigServers: 2 } ) ShardingTaskExecutorPoolRefreshRequirementMS Available for both mongod and mongos. Type: integer Default: 60000 (1 minute) Maximum time the mongos waits before attempting to heartbeat an idle connection in the pool. An idle connection may be discarded during the refresh if the pool is above its minimum size. If set, ShardingTaskExecutorPoolRefreshRequirementMS should be greater than ShardingTaskExecutorPoolRefreshTimeoutMS. Otherwise, mongos adjusts the value of ShardingTaskExecutorPoolRefreshTimeoutMS to be less than ShardingTaskExecutorPoolRefreshRequirementMS. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets ShardingTaskExecutorPoolRefreshRequire- mentMS to 90000 during startup: mongos --setParameter ShardingTaskExecutorPoolRefreshRequirementMS=90000 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolRefreshRequirementMS: 90000 } ) ShardingTaskExecutorPoolRefreshTimeoutMS Available for both mongod and mongos. Type: integer Default: 20000 (20 seconds) Maximum time the mongos waits for a heartbeat before timing out the heartbeat. If set, ShardingTaskExecutorPoolRefreshTimeoutMS should be less than ShardingTaskExecutorPoolRefreshRequirementMS. Otherwise, mongos ad- justs the value of ShardingTaskExecutorPoolRefreshTimeoutMS to be less than ShardingTaskExecutorPoolRefreshRequirementMS. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets ShardingTaskExecutorPoolRefreshTimeoutMS to 30000 during startup: mongos --setParameter ShardingTaskExecutorPoolRefreshTimeoutMS=30000 During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolRefreshTimeoutMS: 30000 } ) ShardingTaskExecutorPoolReplicaSetMatching Available for both mongod and mongos. Type: string Default: "automatic" On a mongos instance, this parameter sets the policy that determines the minimum size limit of its connection pools to nodes within replica sets. On a mongod instance, this parameter sets the policy that determines the minimum size limit of its connection pools to nodes within other replica sets. Note that this parameter only manages connections for operations that are directly related to user requests and CRUD operations. Available values are: * * Matching Policy * Description * * "automatic" (Default) * Starting in 5.0, "automatic" is the new default value. When set for a mongos, the instance follows the behav- ior specified for the "matchPrimaryNode" option. When set for a mongod, the instance follows the behav- ior specified for the "disabled" option. If the ShardingTaskExecutorPoolReplicaSetMatching is set to "automatic", the replicaSetMatchingStrategy still describes the actual policy being used, not "au- tomatic". To find the value of the ShardingTaskExecu- torPoolReplicaSetMatching, use getParameter which re- turns the value of the server parameter. * * "matchPrimaryNode" * When set for a mongos, the minimum size limit of the instance's connection pool to each secondary of a replica set in the sharded cluster (specifically, shard replica set and config servers) is equal to the size of its connection pool to that replica set's primary. When set for a mongod, the minimum size limit of the instance's connection pool to each secondary of another replica set in the sharded cluster (specifically, shard replica set and config servers) is equal to the size of its connection pool to that replica set's primary. If multiple shard servers in your topology can experi- ence a rapid influx of cross-shard operations, do not set this option on your mongod instances. In case of a primary stepdown, matchPrimaryNode ensures that any secondary that becomes the primary can handle the current level of primary reads and writes. * * "matchBusiestNode" * When set for a mongos, the instance's minimum size limit of the connection pool to each member of a replica set in the sharded cluster (specifically, shard replica set and config servers) is equal to the largest among the active connection counts to the primary and each secondary member of that replica set. When set for a mongod, the instance's minimum size limit of the connection pool to each member of another replica set in the sharded cluster (specifically, shard replica set and config servers) is equal to the largest among the active connection counts to the primary and each secondary member of that replica set. With "matchBusiestNode", mongos maintains enough con- nections to each secondary to handle the current level of primary and secondary reads and writes. The number of connections to maintain in the pool decreases as the number of active connections decreases. * * "disabled" * When set for a mongos, the instance's minimum number of connections in the instance's connection pool to each node of a replica set in the sharded clusterv (specifi- cally, shard replica set and config servers) is equal to the ShardingTaskExecutorPoolMinSize. When set for a mongod, the instance's minimum number of connections in the instance's connection pool to each node of another replica set in the sharded cluster (specifically, shard replica set and config servers) is equal to the ShardingTaskExecutorPoolMinSize. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets the ShardingTaskExecutorPoolReplicaSet- Matching to "automatic" during startup: mongod --setParameter ShardingTaskExecutorPoolReplicaSetMatching="automatic" During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, ShardingTaskExecutorPoolReplicaSetMatching: "automatic" } ) taskExecutorPoolSize Available for mongos only. Type: integer Default: 1 The number of Task Executor connection pools to use for a given mon- gos. If the parameter value is 0 or less, the number of Task Executor connection pools is the number of cores with the following excep- tions: * If the number of cores is less than 4, the number of Task Executor connection pools is 4. * If the number of cores is greater than 64, the number of Task Executor connection pools is 64. When running MongoDB 6.2 or newer on Linux, you cannot modify the taskExecutorPoolSize from the default value of 1. You may modify this parameter when running MongoDB on Windows or macOS. The default value of taskExecutorPoolSize is 1: This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting mongos --setParameter taskExecutorPoolSize=6 * ShardingTaskExecutorPoolMaxSize * ShardingTaskExecutorPoolMinSize loadRoutingTableOnStartup Available for mongos only. Type: boolean Default: true Configures a mongos instance to preload the routing table for a sharded cluster on startup. With this setting enabled, the mongos caches the cluster-wide routing table for each sharded collection as part of its startup procedure, before it begins accepting client connections. Without this setting enabled, the mongos only loads a routing table as needed for incoming client connections, and only loads the spe- cific routing table for the namespace of a given request. A mongos instance with the loadRoutingTableOnStartup parameter en- abled may experience longer startup times, but will result in faster servicing of initial client connections once started. loadRoutingTableOnStartup is enabled by default. This parameter is only available at startup. To set the parameter, use the setParameter setting. warmMinConnectionsInShardingTaskExecutorPoolOnStartup Available for mongos only. Type: boolean Default: true Configures a mongos instance to prewarm its connection pool on startup. With this parameter enabled, the mongos attempts to estab- lish ShardingTaskExecutorPoolMinSize network connections to each shard server as part of its startup procedure, before it begins ac- cepting client connections. A timeout for this behavior can be configured with the warmMinCon- nectionsInShardingTaskExecutorPoolOnStartupWaitMS parameter. If this timeout is reached, the mongos will begin accepting client connec- tions regardless of the size of its connection pool. A mongos instance with this parameter enabled may experience longer startup times, but will result in faster servicing of initial client connections once started. warmMinConnectionsInShardingTaskExecutorPoolOnStartup is enabled by default. This parameter is only available at startup. To set the parameter, use the setParameter setting. * warmMinConnectionsInShardingTaskExecutorPoolOnStartupWaitMS * ShardingTaskExecutorPoolMinSize warmMinConnectionsInShardingTaskExecutorPoolOnStartupWaitMS Available for mongos only. Type: integer Default: 2000 (2 seconds) Sets the timeout threshold in milliseconds for a mongos to wait for ShardingTaskExecutorPoolMinSize connections to be established per shard host when using the warmMinConnectionsInShardingTaskExecutor- PoolOnStartup parameter. If this timeout is reached, the mongos will begin accepting client connections regardless of the size of its connection pool. This parameter is only available at startup. To set the parameter, use the setParameter setting. * warmMinConnectionsInShardingTaskExecutorPoolOnStartup * ShardingTaskExecutorPoolMinSize migrateCloneInsertionBatchDelayMS Available for mongod only. Type: Non-negative integer Default: 0 Time in milliseconds to wait between batches of insertions during cloning step of the migration process. This wait is in addition to the secondaryThrottle. The default value of 0 indicates no additional wait. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following sets the migrateCloneInsertionBatchDelayMS to 200 mil- liseconds: mongod --setParameter migrateCloneInsertionBatchDelayMS=200 The parameter may also be set using the setParameter command: db.adminCommand( { setParameter: 1, migrateCloneInsertionBatchDelayMS: 200 } ) migrateCloneInsertionBatchSize Available for mongod only. Type: Non-negative integer Default: 0 The maximum number of documents to insert in a single batch during the cloning step of the migration process. The default value of 0 indicates no maximum number of documents per batch. However, in practice, this results in batches that contain up to 16 MB of documents. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following sets the migrateCloneInsertionBatchSize to 100 docu- ments: mongod --setParameter migrateCloneInsertionBatchSize=100 The parameter may also be set using the setParameter command: db.adminCommand( { setParameter: 1, migrateCloneInsertionBatchSize: 100 } ) orphanCleanupDelaySecs Available for mongod only. Default: 900 (15 minutes) Minimum delay before a migrated chunk is deleted from the source shard. Before deleting the chunk during chunk migration, MongoDB waits for orphanCleanupDelaySecs or for in-progress queries involving the chunk to complete on the shard primary, whichever is longer. However, because the shard primary has no knowledge of in-progress queries run on the shard secondaries, queries that use the chunk but are run on secondaries may see documents disappear if these queries take longer than the time to complete the shard primary queries and the orphanCleanupDelaySecs. This behavior only affects in-progress queries that start before the chunk migration. Queries that start after the chunk migration starts will not use the migrating chunk. If a shard has storage constraints, consider reducing this value temporarily. If running queries that exceed 15 minutes on shard sec- ondaries, consider increasing this value. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following sets the orphanCleanupDelaySecs to 20 minutes: mongod --setParameter orphanCleanupDelaySecs=1200 This may also be set using the setParameter command: db.adminCommand( { setParameter: 1, orphanCleanupDelaySecs: 1200 } ) In all versions, the new value of orphanCleanupDelaySecs is only ap- plied to range deletions created after the value is changed. To ap- ply the new value to existing range deletions, force a step down. persistedChunkCacheUpdateMaxBatchSize Available for mongod only. Type: Integer Default: 1000 To route and serve operations, shards must know the routing and own- ership information associated with their collections. This informa- tion propogates from a shard's primary node to its secondary nodes through the replication of the internal cache collections con- fig.cache.collections and config.cache.chunks.<collectionName>. In previous versions, updates on the chunk cache collection were performed individually (meaning that an entry was deleted and a new entry was inserted). Starting in MongoDB 7.2, these updates are per- formed as a batch of deletions followed by a batch of insertions. The updated logic improves performance for collections that contain a large number of chunks. The persistedChunkCacheUpdateMaxBatchSize parameter specifies the maximum batch size used for updating the persisted chunk cache. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets persistedChunkCacheUpdateMaxBatchSize to 700 at startup: mongod --setParameter persistedChunkCacheUpdateMaxBatchSize=700 You can also set persistedChunkCacheUpdateMaxBatchSize during run- time: db.adminCommand( { setParameter: 1, persistedChunkCacheUpdateMaxBatchSize: 700 } ) rangeDeleterBatchDelayMS Available for mongod only. Type: Non-negative integer Default: 20 The amount of time in milliseconds to wait before the next batch of deletion during the cleanup stage of range migration (or the cleanu- pOrphaned command). The _secondaryThrottle replication delay occurs after each batch deletion. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following sets the rangeDeleterBatchDelayMS to 200 milliseconds: mongod --setParameter rangeDeleterBatchDelayMS=200 The parameter may also be set using the setParameter command: db.adminCommand( { setParameter: 1, rangeDeleterBatchDelayMS: 200 } ) In versions prior to 6.0.3, the new value of rangeDeleterBatchDe- layMS is only applied to range deletions created after the value is changed. To apply the new value to existing range deletions, force a step down. From 6.0.3 on, the new value of the parameter is applied to all the range deletions processed after the update, regardless of when the range deletion was created. rangeDeleterBatchSize Available for mongod only. Type: Non-negative integer Default: 2147483647 starting in MongoDB 5.1.2 and 5.0.6 The maximum number of documents in each batch to delete during the cleanup stage of range migration (or the cleanupOrphaned command). A value of 0 indicates that the system chooses the default value. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets rangeDeleterBatchSize to 32 documents: mongod --setParameter rangeDeleterBatchSize=32 The parameter may also be set using the setParameter command: db.adminCommand( { setParameter: 1, rangeDeleterBatchSize: 32 } ) In versions prior to 6.0.3, the new value of rangeDeleterBatchSize is only applied to range deletions created after the value is changed. To apply the new value to existing range deletions, force a step down. From 6.0.3 on, the new value of the parameter is applied to all the range deletions processed after the update, regardless of when the range deletion was created. rangeDeleterHighPriority Available for mongod only. Type: boolean Default: false When true, prioritizes cleanup of orphaned documents over user oper- ations. By default, this is set to false to prioritize user opera- tions over cleanup of orphaned documents. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets rangeDeleterHighPriority to true: mongod --setParameter rangeDeleterHighPriority=true The parameter may also be set using the setParameter command: db.adminCommand( { setParameter: 1, rangeDeleterBatchSize: true } ) skipShardingConfigurationChecks Available for mongod only. Type: boolean Default: false When true, allows for starting a shard member or config server mem- ber as a standalone for maintenance operations. This parameter is mutually exclusive with the --configsvr or --shardsvr options. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongod --setParameter skipShardingConfigurationChecks=true Once maintenance has completed, remove the skipShardingConfigura- tionChecks parameter when restarting the mongod. findChunksOnConfigTimeoutMS Available for both mongod and mongos. Type: Non-negative integer Default: 900000 The timeout in milliseconds for find operations on chunks. If there is a large number of chunks in the cluster and chunk load- ing fails with the error ExceededTimeLimit, increase the parameter value: mongod --setParameter findChunksOnConfigTimeoutMS=1000000 This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting HEALTH MANAGER PARAMETERS activeFaultDurationSecs Available for mongos only. Type: Document The amount of time to wait from a Health Managers Overview failure until the mongos is removed from the cluster, in seconds. When a failure is detected and a Health Manager is configured as critical, the server waits for the specified interval before remov- ing the mongos from the cluster. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For example, to set the duration from failure to crash to five min- utes, issue the following at startup: mongos --setParameter activeFaultDurationSecs=300 Or if using the setParameter command in a mongosh session that is connected to a running mongos: db.adminCommand( { setParameter: 1, activeFaultDurationSecs: 300 } ) Parameters set with setParameter do not persist across restarts. See the setParameter page for details. To make this setting persistent, set activeFaultDurationSecs in your mongos config file using the setParameter option as in the following example: setParameter: activeFaultDurationSecs: 300 healthMonitoringIntensities Available for mongos only. Type: Array of documents Use this parameter to set intensity levels for Health Managers. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting healthMonitoringIntensities accepts an array of documents, values. Each document in values takes two fields: * type, the Health Manager facet * intensity, the intensity level HEALTH MANAGERS * * Facet * What the Health Observer Checks * * configServer * Cluster health issues related to connectivity to the config server. * * dns * Cluster health issues related to DNS availability and func- tionality. * * ldap * Cluster health issues related to LDAP availability and func- tionality. INTENSITY LEVELS * * Intensity Level * Description * * critical * The Health Manager on this facet is enabled and has the abil- ity to move the failing mongos out of the cluster if an error occurs. The Health Manager waits the amount of time specified by activeFaultDurationSecs before stopping and moving the mon- gos out of the cluster automatically. * * non-critical * The Health Manager on this facet is enabled and logs errors, but the mongos remains in the cluster if errors are encoun- tered. * * off * The Health Manager on this facet is disabled. The mongos does not perform any health checks on this facet. This is the de- fault intensity level. For example, to set the dns Health Manager facet to the critical intensity level, issue the following at startup: mongos --setParameter 'healthMonitoringIntensities={ values:[ { type:"dns", intensity: "critical"} ] }' Or if using the setParameter command in a mongosh session that is connected to a running mongos: db.adminCommand( { setParameter: 1, healthMonitoringIntensities: { values: [ { type: "dns", intensity: "critical" } ] } } ) } ) Parameters set with setParameter do not persist across restarts. See the setParameter page for details. To make this setting persistent, set healthMonitoringIntensities in your mongos config file using the setParameter option as in the following exam- ple: setParameter: healthMonitoringIntensities: "{ values:[ { type: healthMonitoringIntervals Available for mongos only. Type: Array of documents How often this Health Manager will run, in milliseconds. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting healthMonitoringIntervals accepts an array of documents, values. Each document in values takes two fields: * type, the Health Manager facet * interval, the time interval it runs at, in milliseconds HEALTH MANAGERS * * Facet * What the Health Observer Checks * * configServer * Cluster health issues related to connectivity to the config server. * * dns * Cluster health issues related to DNS availability and func- tionality. * * ldap * Cluster health issues related to LDAP availability and func- tionality. For example, to set the ldap Health Manager facet to the run health checks every 30 seconds, issue the following at startup: mongos --setParameter 'healthMonitoringIntervals={ values:[ { type:"ldap", interval: "30000"} ] }' Or if using the setParameter command in a mongosh session that is connected to a running mongos: db.adminCommand( { setParameter: 1, healthMonitoringIntervals: { values: [ { type: "ldap", interval: "30000" } ] } } ) } ) Parameters set with setParameter do not persist across restarts. See the setParameter page for details. To make this setting persistent, set healthMonitoringIntervals in your mon- gos config file using the setParameter option as in the following example: setParameter: healthMonitoringIntervals: "{ values: [{type: progressMonitor Available for mongos only. Type: Document Progress Monitor runs tests to ensure that Health Manager checks do not become stuck or unresponsive. Progress Monitor runs these tests in intervals specified by interval. If a health check begins but does not complete within the timeout given by deadline, Progress Monitor stops the mongos and removes it from the cluster. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting PROGRESSMONITOR FIELDS * * Field * Description * Units * * interval * How often to ensure Health Managers are not stuck or unrespon- sive. * Milliseconds * * deadline * Timeout before automatically failing the mongos if a Health Manager check is not making progress. * Seconds To set the interval to 1000 milliseconds and the deadline to 300 seconds, issue the following at startup: mongos --setParameter 'progressMonitor={"interval": 1000, "deadline": 300}' Or if using the setParameter command in a mongosh session that is connected to a running mongos: db.adminCommand( { setParameter: 1, progressMonitor: { interval: 1000, deadline: 300 } ) } ) Parameters set with setParameter do not persist across restarts. See the setParameter page for details. To make this setting persistent, set progressMonitor in your mongos config file using the setParameter option as in the following example: setParameter: progressMonitor: "{ interval: 1000, deadline: 300 }" STORAGE PARAMETERS honorSystemUmask Available for mongod only. Default: false If honorSystemUmask is set to true, new files created by MongoDB have permissions in accordance with the user's umask settings. You cannot set processUmask if honorSystemUmask is set to true. If honorSystemUmask is set to false, new files created by MongoDB have permissions set to 600, which gives read and write permissions only to the owner. New directories have permissions set to 700. You can use processUmask to override the default permissions for groups and other users on all new files created by MongoDB. This parameter is only available at startup. To set the parameter, use the setParameter setting. mongod --setParameter honorSystemUmask=true honorSystemUmask is not available on Windows systems. journalCommitInterval Available for mongod only. Specify an integer between 1 and 500 signifying the number of mil- liseconds (ms) between journal commits. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting Consider the following example which sets the journalCommitInterval to 200 ms: db.adminCommand( { setParameter: 1, journalCommitInterval: 200 } ) storage.journal.commitIntervalMs minSnapshotHistoryWindowInSeconds Available for mongod only. Default: 300 The minimum time window in seconds for which the storage engine keeps the snapshot history. If you query data using read concern "snapshot" and specify an atClusterTime value older than the speci- fied minSnapshotHistoryWindowInSeconds, mongod returns a Snapshot- TooOld error. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting Specify an integer greater than or equal to (>=) 0. Consider the following example which sets the minSnapshotHistoryWin- dowInSeconds to 600 seconds: db.adminCommand( { setParameter: 1, minSnapshotHistoryWindowInSeconds: 600 } ) Increasing the value of minSnapshotHistoryWindowInSeconds increases disk usage. For more information, see Snapshot History Retention. To modify this value for a MongoDB Atlas (https://www.mon- godb.com/docs/atlas/) cluster, you must contact Atlas Support (https://www.mongodb.com/docs/atlas/support/). processUmask Available for mongod only. Overrides the default permissions used for groups and other users when honorSystemUmask is set to false. By default, when honorSyste- mUmask is set to false, new files created by MongoDB have permis- sions set to 600. Use the processUmask parameter to override this default with a custom umask value. The file owner inherits permis- sions from the system umask. This parameter is only available at startup. To set the parameter, use the setParameter setting. You cannot set this parameter if honorSystemUmask is set to true. Consider the following example, which sets the permissions for groups and other users to read/write only and retains the system umask settings for the owner: mongod --setParameter processUmask=011 processUmask is not available on Windows systems. storageEngineConcurrentReadTransactions Available for mongod only. Type: integer Default: 128 Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only. Specify the maximum number of concurrent read transactions (read tickets) allowed into the storage engine. If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128. Starting in MongoDB 7.0, if you set storageEngineConcurrentRead- Transactions to a non-default value, it disables an algorithm that dynamically adjusts the number of concurrent storage engine transac- tions. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting db.adminCommand( { setParameter: 1, storageEngineConcurrentReadTransactions: <int> } ) The wiredTigerConcurrentReadTransactions parameter was renamed to storageEngineConcurrentReadTransactions. wiredTiger.concurrentTransactions storageEngineConcurrentWriteTransactions Available for mongod only. Type: integer Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only. Specify the maximum number of concurrent write transactions allowed into the WiredTiger storage engine. By default, MongoDB sets storageEngineConcurrentWriteTransactions to whichever value is higher: * Number of cores on the machine running MongoDB * 4 If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128. Starting in MongoDB 7.0, if you set storageEngineConcurrentWrite- Transactions to a non-default value, it disables an algorithm that dynamically adjusts the number of concurrent storage engine transac- tions. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting db.adminCommand( { setParameter: 1, storageEngineConcurrentWriteTransactions: <int> } ) The wiredTigerConcurrentWriteTransactions parameter was renamed to storageEngineConcurrentWriteTransactions. wiredTiger.concurrentTransactions syncdelay Available for mongod only. Specify the interval in seconds when mongod flushes its working mem- ory to disk. By default, mongod flushes memory to disk every 60 sec- onds. In almost every situation you should not set this value and use the default setting. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting Consider the following example which sets the syncdelay to 60 sec- onds: db.adminCommand( { setParameter: 1, syncdelay: 60 } ) To provide durable data, WiredTiger uses checkpoints. For more de- tails, see Journaling and the WiredTiger Storage Engine. * journalCommitInterval * storage.syncPeriodSecs temporarilyUnavailableBackoffBaseMs Available for mongod only. Specifies the initial delay before retying a write operation that was rolled back due to cache pressure. In rare circumstances, a write can fail due to cache pressure. When this happens MongoDB issues a TemporarilyUnavailable error and in- crements the temporarilyUnavailableErrors counter in two places: the slow query log and the Full Time Diagnostic Data Capture (FTDC). Individual operations within multi-document transactions never re- turn TemporarilyUnavailable errors. Adjust the write retry properties by modifying the temporarilyU- navailableBackoffBaseMs and temporarilyUnavailableMaxRetries parame- ters. The parameter accepts: * * Value * Description * * integer >= 0 * Defaults to 1 second. The initial delay between re- tries. The value increases with each retry to a maximum of 55 seconds. A larger value increases the chance that the cache pressure will be reduced before the next retry. To configure number of retries, use temporarilyUnavail- ableMaxRetries. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting To set a new value, use db.adminCommand(): db.adminCommand( { setParameter: 1, temporarilyUnavailableBackoffBaseMs: 3 } ) temporarilyUnavailableMaxRetries Available for mongod only. Specifies the maximum number of retries when a write operation is rolled back due to cache pressure. In rare circumstances, a write can fail due to cache pressure. When this happens MongoDB issues a TemporarilyUnavailable error and in- crements the temporarilyUnavailableErrors counter in two places: the slow query log and the Full Time Diagnostic Data Capture (FTDC). Individual operations within multi-document transactions never re- turn TemporarilyUnavailable errors. Adjust the write retry properties by modifying the temporarilyU- navailableBackoffBaseMs and temporarilyUnavailableMaxRetries parame- ters. The parameter accepts: * * Value * Description * * integer >= 0 * Defaults to 10. The maximum number of retries. There is an increasing delay between retries. To con- figure the backoff time, use temporarilyUnavailable- BackoffBaseMs. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting To set a new value, use db.adminCommand(): db.adminCommand( { setParameter: 1, temporarilyUnavailableMaxRetries: 5 } ) WIREDTIGER PARAMETERS wiredTigerConcurrentReadTransactions Available for mongod only. Type: integer Default: 128 Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only. Specify the maximum number of concurrent read transactions (read tickets) allowed into the storage engine. If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128. Starting in MongoDB 7.0, if you set wiredTigerConcurrentReadTransac- tions to a non-default value, it disables an algorithm that dynami- cally adjusts the number of concurrent storage engine transactions. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting db.adminCommand( { setParameter: 1, wiredTigerConcurrentReadTransactions: <int> } ) wiredTiger.concurrentTransactions wiredTigerConcurrentWriteTransactions Available for mongod only. Type: integer Starting in MongoDB 7.0, this parameter is available for all storage engines. In earlier versions, this parameter is available for the WiredTiger storage engine only. Specify the maximum number of concurrent write transactions allowed into the WiredTiger storage engine. By default, MongoDB sets wiredTigerConcurrentWriteTransactions to whichever value is higher: * Number of cores on the machine running MongoDB * 4 If you use the default value, MongoDB dynamically adjusts the number of tickets to optimize performance, with a highest possible value of 128. Starting in MongoDB 7.0, if you set wiredTigerConcurrentWriteTrans- actions to a non-default value, it disables an algorithm that dynam- ically adjusts the number of concurrent storage engine transactions. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting db.adminCommand( { setParameter: 1, wiredTigerConcurrentWriteTransactions: <int> } ) wiredTiger.concurrentTransactions wiredTigerEngineRuntimeConfig Available for mongod only. Specify wiredTiger storage engine configuration options for a run- ning mongod instance. This parameter is only available at runtime. To set the parameter, use the setParameter command. Avoid modifying the wiredTigerEngineRuntimeConfig unless under the direction from MongoDB engineers as this setting has major implica- tion across both WiredTiger and MongoDB. Consider the following operation prototype: db.adminCommand({ "setParameter": 1, "wiredTigerEngineRuntimeConfig": "<option>=<setting>,<option>=<setting>" }) wiredTigerFileHandleCloseIdleTime Available for mongod only. Type: integer Default: 600 Specifies the amount of time in seconds that a file handle in wiredTiger can remain idle before being closed. If you set wiredTigerFileHandleCloseIdleTime to 0, idle handles are not closed. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example: mongod --setParameter wiredTigerFileHandleCloseIdleTime=100000 See the WiredTiger documentation for all available WiredTiger configuration options (http://source.wiredtiger.com/mon- godb-5.0/struct_w_t___c_o_n_n_e_c_t_i_o_n.html#). AUDITING PARAMETERS auditAuthorizationSuccess Available for both mongod and mongos. Type: boolean Default: false Available only in MongoDB Enterprise (http://www.mongodb.com/prod- ucts/mongodb-enterprise-advanced?tck=docs_server) and MongoDB Atlas (https://cloud.mongodb.com/user#/atlas/login). Enables the auditing of authorization successes for the authCheck action. When auditAuthorizationSuccess is false, the audit system only logs the authorization failures for authCheck. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting To enable the audit of authorization successes, issue the following command: db.adminCommand( { setParameter: 1, auditAuthorizationSuccess: true } ) Enabling auditAuthorizationSuccess degrades performance more than logging only the authorization failures. If runtime audit configuration is enabled, the auditAuthorization- Success parameter should not appear in the mongod or mongos configu- ration file. The server will fail to start if the parameter is present. getParameter auditConfigPollingFrequencySecs Type: integer Default: 300 A sharded cluster may have servers which maintain audit configura- tion settings for the cluster. Set the interval, in seconds, for non-configured servers to poll a config server for the current audit generation. If this value returned differs from the previously known value, the initiating node will request the current configuration and update its internal state. Using the default value of 300 seconds, non-config nodes may lag up to 5 minutes after you set the auditConfig cluster parameter. This parameter is only available at startup. To set the parameter, use the setParameter setting. auditEncryptionHeaderMetadataFile Available for both mongod and mongos. Type: string Available only in MongoDB Enterprise (http://www.mongodb.com/prod- ucts/mongodb-enterprise-advanced?tck=docs_server). MongoDB Enter- prise and Atlas have different configuration requirements. Path and file name for logging metadata audit headers for audit log encryption. A header is placed at the top of each audit log file and contains metadata for decrypting the audit log. The headers are also stored in the audit log. This parameter is only available at startup. To set the parameter, use the setParameter setting. For example, the following sets the path and file for auditEncryp- tionHeaderMetadataFile: mongod --setParameter auditEncryptionHeaderMetadataFile=/auditFiles/auditHeadersMetadataFile.log auditEncryptKeyWithKMIPGet Available for both mongod and mongos. Type: boolean Default: false Available only in MongoDB Enterprise (http://www.mongodb.com/prod- ucts/mongodb-enterprise-advanced?tck=docs_server). MongoDB Enter- prise and Atlas have different configuration requirements. Enables audit log encryption for Key Management Interoperability Protocol (KMIP) servers that only support KMIP protocol version 1.0 or 1.1. This parameter is only available at startup. To set the parameter, use the setParameter setting. The following example sets auditEncryptKeyWithKMIPGet to true: mongod --setParameter auditEncryptKeyWithKMIPGet=true TRANSACTION PARAMETERS coordinateCommitReturnImmediatelyAfterPersistingDecision Updated in version 6.1 Available for mongod only. Type: boolean Default: false * When set to false, the shard transaction coordinator waits for all participating shards to acknowledge the decision to either commit or cancel a multi-document transaction before returning the result to the client. * When set to true, the shard transaction coordinator returns a multi-document transaction commit decision to the client as soon as the decision is made durable with the requested transaction write concern. If the client requested a write concern that is less than "majority", the commit may roll back after the decision is returned to the client. Transactions may not have "read your writes" consistency. That is, a read operation may not show the results of write operations that preceded it. This can happen if: * A transaction has to write to multiple shards. * The read and the earlier write take place in different sessions. Causal consistency only guarantees the causal relationship of reads and writes that occur within the same session. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets coordinateCommitReturnImmediatelyAfter- PersistingDecision to true: mongod --setParameter coordinateCommitReturnImmediatelyAfterPersistingDecision=true During run time, you can also set the parameter with the setParame- ter command: db.adminCommand( { setParameter: 1, coordinateCommitReturnImmediatelyAfterPersistingDecision: true } ) internalSessionsReapThreshold Available for both mongod and mongos. Default: 1000 Session limit for internal session metadata deletion. The metadata: * Contains session transaction information for user opera- tions. * Is stored in the config.transactions collection. When the number of internal sessions is greater than internalSes- sionsReapThreshold, the metadata is deleted. If you set internalSessionsReapThreshold to 0, the internal session metadata is only deleted when the user session ends. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following example sets internalSessionsReapThreshold to 500 ses- sions: db.adminCommand( { setParameter: 1, internalSessionsReapThreshold: 500 } ) You can also set internalSessionsReapThreshold at startup. For exam- ple: mongod --setParameter internalSessionsReapThreshold=500 transactionLifetimeLimitSeconds Available for mongod only. Default: 60 Specifies the lifetime of multi-document transactions. Transactions that exceed this limit are considered expired and will be aborted by a periodic cleanup process. The cleanup process runs every transac- tionLifetimeLimitSeconds/2 seconds or at least once every 60 sec- onds. The cleanup process helps relieve storage cache pressure. The minimum value for transactionLifetimeLimitSeconds is 1 second. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following sets the transactionLifetimeLimitSeconds to 30 sec- onds: db.adminCommand( { setParameter: 1, transactionLifetimeLimitSeconds: 30 } ) You can also set parameter transactionLifetimeLimitSeconds at startup time. mongod --setParameter "transactionLifetimeLimitSeconds=30" To set the parameter for a sharded cluster, the parameter must be modified for all shard replica set members. Starting in MongoDB 5.0, if you change the transactionLifetimeLimit- Seconds parameter, you must also change transactionLifetimeLimitSec- onds to the same value on all config server replica set members. Keeping this value consistent: * Ensures the routing table history is retained for at least as long as the transaction lifetime limit on the shard replica set members. * Reduces the transaction retry frequency and therefore im- proves performance. transactionTooLargeForCacheThreshold Available for mongod only. Type: decimal Default: 0.75 The threshold value for retrying transactions that fail due to cache pressure. The value is a percentage of the dirty cache size. The de- fault value, 0.75, means 75% of the dirty cache. The dirty cache is limited to 20% of the total cache size. When transactionTooLargeForCacheThreshold is set to 0.75, the server only retries transactions that use less than 15% (0.75 * 20%) of the to- tal storage engine cache. The limit only applies to retries. Large transactions can use more than transactionTooLargeForCacheThreshold percent of the dirty cache. However, if a large transaction is rolled back due to cache pressure, the server issues a TransactionTooLargeForCache error and does not retry the transaction. To disable this behavior, set transactionTooLargeForCacheThreshold to 1.0. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting For more information on WiredTiger storage, see: storage.wiredTiger Options. maxTransactionLockRequestTimeoutMillis Available for mongod only. Type: integer Default: 5 The maximum amount of time in milliseconds that multi-document transactions should wait to acquire locks required by the operations in the transaction. If the transaction cannot acquire the locks after waiting maxTrans- actionLockRequestTimeoutMillis, the transaction aborts. By default, multi-document transactions wait 5 milliseconds. That is, if the transaction cannot acquire the locks within 5 millisec- onds, the transaction aborts. If an operation provides a greater timeout in a lock request, maxTransactionLockRequestTimeoutMillis overrides the operation-specific timeout. You can set maxTransactionLockRequestTimeoutMillis to: * 0 such that if the transaction cannot acquire the required locks immediately, the transaction aborts. * A number greater than 0 to wait the specified time to ac- quire the required locks. This can help obviate transaction aborts on momentary concurrent lock acquisitions, like fast-running metadata operations. However, this could pos- sibly delay the abort of deadlocked transaction operations. * -1 to use the operation specific timeout. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following sets the maxTransactionLockRequestTimeoutMillis to 20 milliseconds: db.adminCommand( { setParameter: 1, maxTransactionLockRequestTimeoutMillis: 20 } ) You can also set this parameter during start-up: mongod --setParameter maxTransactionLockRequestTimeoutMillis=20 SLOT-BASED EXECUTION PARAMETERS planCacheSize Available for mongod only. Type: string Default: 5% Although the planCacheSize parameter existed in prior versions of MongoDB, it had no effect on the plan cache until version 6.3. Sets the size of the plan cache only for the slot-based query execu- tion engine. You can set the planCacheSize value to either: * A percentage of the system's total physical memory to allo- cate for the plan cache. For example, "8.5%". * The exact amount of data to allocate for the plan cache in either MB or GB. For example, "100MB" or "1GB". Increasing the plan cache size adds more cached query shapes for the query planner. This can improve query performance, but increases memory usage. This parameter is available both at runtime and at startup: * To set the parameter at runtime, use the setParameter com- mand * To set the parameter at startup, use the setParameter set- ting The following startup command sets planCacheSize to 80 megabytes: mongod --setParameter planCacheSize="80MB" You can also use the setParameter command within the MongoDB Shell (https://www.mongodb.com/docs/mongodb-shell/): db.adminCommand( { setParameter: 1, planCacheSize: "80MB" } ) mongodb-parameters(5)
MONGODB SERVER PARAMETERS | SYNOPSIS | PARAMETERS
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