ALTER SYSTEM

7 SQL - Language Statements

ALTER SYSTEM

change a server configuration parameter

    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 runtime-config.

`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 guc-data-directory, guc-allow-alter-system, nor parameters that are not allowed in `postgresql.conf` (e.g., preset options).

See config-setting for other ways to set the parameters.

`ALTER SYSTEM` can be disabled by setting guc-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

- sql-set
- sql-show