WAL Archiving

Write Ahead Log (WAL) is also called Xlog. The parameter wal_level specifies the level of information to be written into a WAL. To enable read-only queries on a standby node, you need to set the wal_level parameter to hot_standby on the primary node and hot_standby to on on the standby node. In a distributed environment, hot_standby cannot be set to off and wal_level cannot be set to archive or minimal. Otherwise, a database cannot be started. You are advised to use the default value (hot_standby) of wal_level.