Parameters

Replication

26 PostgreSQL 18.6 parameters. Each one has its own animation and explanation.

Primary Server

synchronized_standby_slots: Physical slots logical decoding must wait for, so failover never leaves subscribers ahead.
synchronous_standby_names: Which standbys COMMIT must wait for: FIRST n by priority, or ANY n as a quorum.

idle_replication_slot_timeout: New in 18: invalidate replication slots that have been inactive longer than this.
max_replication_slots: How many replication slots (physical or logical) can exist on this server.
max_slot_wal_keep_size: Cap on WAL a replication slot may hold. Past it, the slot is invalidated to save the disk.
max_wal_senders: How many WAL sender processes (standbys, pg_basebackup, logical subscribers) may run.
output_plugin_libraries: Allow-list of libraries that may be used as logical decoding output plugins.
track_commit_timestamp: Record the commit time of every transaction (needed for some conflict handling).
wal_keep_size: Extra WAL kept in pg_wal for standbys that do not use a replication slot.
wal_sender_timeout: Drop a replication connection that has been silent for this long.

hot_standby: Allow read-only queries on a standby while it replays WAL.
hot_standby_feedback: Standby tells the primary which rows its queries still need, to avoid query cancellations.
max_standby_archive_delay: Like max_standby_streaming_delay, for WAL restored from the archive.
max_standby_streaming_delay: How long replay may wait for conflicting standby queries before cancelling them.
primary_conninfo: Connection string a standby uses to stream WAL from its primary.
primary_slot_name: Physical replication slot the standby uses on the primary, so needed WAL is kept.
recovery_min_apply_delay: Keep a standby deliberately behind by this long, as protection against mistakes.
sync_replication_slots: Standby keeps copies of the primary's failover logical slots, so subscribers survive failover.
wal_receiver_create_temp_slot: Let the WAL receiver create a temporary slot when primary_slot_name is not set.
wal_receiver_status_interval: How often the standby reports its write/flush/replay position to the primary.
wal_receiver_timeout: Standby drops a replication connection after this long without hearing from the primary.
wal_retrieve_retry_interval: How long a standby waits before trying again when no new WAL is available anywhere.

max_active_replication_origins: New in 18: how many replication origins (subscriptions) can be tracked at once.
max_logical_replication_workers: Total logical replication workers on a subscriber: apply, table sync and parallel apply.
max_parallel_apply_workers_per_subscription: Parallel apply workers one subscription may use for large streamed transactions.
max_sync_workers_per_subscription: How many tables one subscription copies in parallel during initial synchronization.