ALTER SYSTEM ALTER SYSTEM 7 SQL - Language Statements ALTER SYSTEM change a server configuration parameter ALTER SYSTEM SET configuration_parameter { TO | = } { value | 'value' | DEFAULT } ALTER SYSTEM RESET configuration_parameter ALTER SYSTEM RESET ALL ALTER SYSTEM writes the configuration parameter values to the postgresql.auto.conf file. Setting the parameter to DEFAULT, or using the RESET variant, removes the configuration entry from postgresql.auto.conf file. Use RESET ALL to clear all configuration entries. The values will be effective after reload of server configuration (SIGHUP) or in next server start based on the type of configuration parameter modified. This command is not allowed inside transaction block or function. See for other ways to set the parameters and how they become effective. configuration_parameter Name of a settable run-time parameter. Available parameters are documented in . value New value of 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 to remove the parameter and its value from postgresql.auto.conf This command can't be used to set and any parameters (e.g., preset options) that are not allowed in postgresql.conf. Set the wal_level: ALTER SYSTEM SET wal_level = hot_standby; Set the authentication_timeout: ALTER SYSTEM SET authentication_timeout = 10; The ALTER SYSTEM statement is a PostgreSQL extension.