'\" t
.\"     Title: ALTER SYSTEM
.\"    Author: The PostgreSQL Global Development Group
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 2021
.\"    Manual: PostgreSQL 13.4 Documentation
.\"    Source: PostgreSQL 13.4
.\"  Language: English
.\"
.TH "ALTER SYSTEM" "7" "2021" "PostgreSQL 13.4" "PostgreSQL 13.4 Documentation"
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.SH "NAME"
ALTER_SYSTEM \- change a server configuration parameter
.SH "SYNOPSIS"
.sp
.nf
ALTER SYSTEM SET \fIconfiguration_parameter\fR { TO | = } { \fIvalue\fR | \*(Aq\fIvalue\fR\*(Aq | DEFAULT }

ALTER SYSTEM RESET \fIconfiguration_parameter\fR
ALTER SYSTEM RESET ALL
.fi
.SH "DESCRIPTION"
.PP
\fBALTER SYSTEM\fR
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\&.
\fBALTER SYSTEM\fR
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
\fBRESET\fR
variant, removes that configuration entry from the
postgresql\&.auto\&.conf
file\&. Use
RESET ALL
to remove all such configuration entries\&.
.PP
Values set with
\fBALTER SYSTEM\fR
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
\fBpg_reload_conf()\fR, running
pg_ctl reload, or sending a
SIGHUP
signal to the main server process\&.
.PP
Only superusers can use
\fBALTER SYSTEM\fR\&. 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\&.
.SH "PARAMETERS"
.PP
\fIconfiguration_parameter\fR
.RS 4
Name of a settable configuration parameter\&. Available parameters are documented in
Chapter\ \&19\&.
.RE
.PP
\fIvalue\fR
.RS 4
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\&.
DEFAULT
can be written to specify removing the parameter and its value from
postgresql\&.auto\&.conf\&.
.RE
.SH "NOTES"
.PP
This command can\*(Aqt be used to set
data_directory, nor parameters that are not allowed in
postgresql\&.conf
(e\&.g\&.,
preset options)\&.
.PP
See
Section\ \&19.1
for other ways to set the parameters\&.
.SH "EXAMPLES"
.PP
Set the
wal_level:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER SYSTEM SET wal_level = replica;
.fi
.if n \{\
.RE
.\}
.PP
Undo that, restoring whatever setting was effective in
postgresql\&.conf:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER SYSTEM RESET wal_level;
.fi
.if n \{\
.RE
.\}
.SH "COMPATIBILITY"
.PP
The
\fBALTER SYSTEM\fR
statement is a
PostgreSQL
extension\&.
.SH "SEE ALSO"
\fBSET\fR(7), \fBSHOW\fR(7)