ALTER SYSTEM
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## ALTER SYSTEM

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, SHOW

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