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ALTER SYSTEM(7)		 PostgreSQL 17.5 Documentation	       ALTER SYSTEM(7)

NAME
       ALTER_SYSTEM - change a server configuration parameter

SYNOPSIS
       ALTER SYSTEM SET	configuration_parameter	{ TO | = } { value [, ...] | DEFAULT }

       ALTER SYSTEM RESET configuration_parameter
       ALTER SYSTEM RESET ALL

DESCRIPTION
       ALTER SYSTEM is used for	changing server	configuration parameters
       across the entire database cluster. It can be more convenient than the
       traditional method of manually editing the postgresql.conf file.	 ALTER
       SYSTEM writes the given parameter setting to the	postgresql.auto.conf
       file, which is read in addition to postgresql.conf. Setting a parameter
       to DEFAULT, or using the	RESET variant, removes that configuration
       entry from the postgresql.auto.conf file. Use RESET ALL to remove all
       such configuration entries.

       Values set with ALTER SYSTEM will be effective after the	next server
       configuration reload, or	after the next server restart in the case of
       parameters that can only	be changed at server start. A server
       configuration reload can	be commanded by	calling	the SQL	function
       pg_reload_conf(), running pg_ctl	reload,	or sending a SIGHUP signal to
       the main	server process.

       Only superusers and users granted ALTER SYSTEM privilege	on a parameter
       can change it using ALTER SYSTEM. Also, since this command acts
       directly	on the file system and cannot be rolled	back, it is not
       allowed inside a	transaction block or function.

PARAMETERS
       configuration_parameter
	   Name	of a settable configuration parameter. Available parameters
	   are documented in Chapter 19.

       value
	   New value of	the parameter. Values can be specified as string
	   constants, identifiers, numbers, or comma-separated lists of	these,
	   as appropriate for the particular parameter.	Values that are
	   neither numbers nor valid identifiers must be quoted.  DEFAULT can
	   be written to specify removing the parameter	and its	value from
	   postgresql.auto.conf.

	   For some list-accepting parameters, quoted values will produce
	   double-quoted output	to preserve whitespace and commas; for others,
	   double-quotes must be used inside single-quoted strings to get this
	   effect.

NOTES
       This command can't be used to set data_directory, allow_alter_system,
       nor parameters that are not allowed in postgresql.conf (e.g., preset
       options).

       See Section 19.1	for other ways to set the parameters.

       ALTER SYSTEM can	be disabled by setting allow_alter_system to off, but
       this is not a security mechanism	(as explained in detail	in the
       documentation for this parameter).

EXAMPLES
       Set the wal_level:

	   ALTER SYSTEM	SET wal_level =	replica;

       Undo that, restoring whatever setting was effective in postgresql.conf:

	   ALTER SYSTEM	RESET wal_level;

COMPATIBILITY
       The ALTER SYSTEM	statement is a PostgreSQL extension.

SEE ALSO
       SET(7), SHOW(7)

PostgreSQL 17.5			     2025		       ALTER SYSTEM(7)

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