wal_level determines how much information is written to the WAL. The default value is
replica, which writes enough data to support WAL archiving and replication, including running read-only queries on a standby server.
minimal removes all logging except the information required to recover from a crash or immediate shutdown. Finally,
logical adds information necessary to support logical decoding. Each level includes the information logged at all lower levels. This parameter can only be set at server start.
minimal level generates the least WAL volume. It logs no row information for permanent relations in transactions that create or rewrite them. This can make operations much faster (see populate-pitr). Operations that initiate this optimization include:
- ALTER ... SET TABLESPACE
- CREATE TABLE
- REFRESH MATERIALIZED VIEW (without CONCURRENTLY)
replicaor higher must be used to enable continuous archiving (archive_mode) and streaming binary replication. In fact, the server will not even start in this mode if max_wal_senders is non-zero. Note that changing
minimalmakes previous base backups unusable for point-in-time recovery and standby servers.
logical level, the same information is logged as with
replica, plus information needed to extract logical change sets from the WAL. Using a level of
logical will increase the WAL volume, particularly if many tables are configured for
REPLICA IDENTITY FULL and many UPDATE and DELETE statements are executed.
In releases prior to 9.6, this parameter also allowed the values
hot_standby. These are still accepted but mapped to