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4.5.5 Standby Servers

These settings control the behavior of a standby server that is to receive replication data.

hot_standby (boolean)

Specifies whether or not you can connect and run queries during recovery, as described in section 11.5 Hot Standby. The default value is off. This parameter can only be set at server start. It only has effect during archive recovery or in standby mode.

max_standby_archive_delay (integer)

When Hot Standby is active, this parameter determines how long the standby server should wait before canceling standby queries that conflict with about-to-be-applied WAL entries, as described in section 11.5.2 Handling query conflicts. max_standby_archive_delay applies when WAL data is being read from WAL archive (and is therefore not current). The default is 30 seconds. Units are milliseconds if not specified. A value of -1 allows the standby to wait forever for conflicting queries to complete. This parameter can only be set in the ‘postgresql.conf’ file or on the server command line. Note that max_standby_archive_delay is not the same as the maximum length of time a query can run before cancellation; rather it is the maximum total time allowed to apply any one WAL segment's data. Thus, if one query has resulted in significant delay earlier in the WAL segment, subsequent conflicting queries will have much less grace time.

max_standby_streaming_delay (integer)

When Hot Standby is active, this parameter determines how long the standby server should wait before canceling standby queries that conflict with about-to-be-applied WAL entries, as described in section 11.5.2 Handling query conflicts. max_standby_streaming_delay applies when WAL data is being received via streaming replication. The default is 30 seconds. Units are milliseconds if not specified. A value of -1 allows the standby to wait forever for conflicting queries to complete. This parameter can only be set in the ‘postgresql.conf’ file or on the server command line. Note that max_standby_streaming_delay is not the same as the maximum length of time a query can run before cancellation; rather it is the maximum total time allowed to apply WAL data once it has been received from the primary server. Thus, if one query has resulted in significant delay, subsequent conflicting queries will have much less grace time until the standby server has caught up again.