max_active_replication_origins

max_active_replication_origins — Sets the maximum number of active replication origins. Observed in PG18–19 Beta 3; its last measured boot default is 10 in PG19 Beta 3, with postmaster context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.

Note

Fact — official short description: “Sets the maximum number of active replication origins.”

Identity

Type , Valueinteger: Upstream pg_settings type
Context , Valuepostmaster: Requires a server restart
Unit , Value—: Raw unit
Range , Value0 – 262143: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueReplication / Subscribers: Upstream classification
Latest boot value , Value10: 10

Lifecycle

Fact	Value
First observed	PG18
Present in	PG18–19 Beta 3
Removed in	No
Introduction commit	`04ff636cbce4` — Add GUC option to control maximum active replication origins.
Commit date	2025-03-21
Discussion	thread 1

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG18–19 Beta 3	`10`	—	10

How it works

Sets the maximum number of active replication origins. The value is fixed when the server starts, so changing it requires a restart.

Each active logical replication origin tracks remote progress so apply can avoid replaying changes twice. The startup allocation effectively bounds concurrently active subscriptions/origins and consumes shared resources even though dormant catalog rows need not all be active.

Monitor and change max_active_replication_origins together with max_logical_replication_workers, max_replication_slots, track_commit_timestamp. Validate on the relevant server role and real workload, then use its postmaster context to choose session change, reload, or restart; a historical boot default is not the current effective value.

Tuning advice

Tip

Advice. These are workload-specific starting points and must be validated with measurements.

Workload	Guidance
OLTP	Size max_active_replication_origins from topology, failover roles, slot/subscription count, and reconnect headroom. Test worst-case primary latency, standby replay, and disk retention before production.
OLAP	Read standbys and logical subscribers often see long queries or large transactions. Put explicit bounds on replay/apply and monitor lag, worker saturation, slot restart_lsn, and conflict cancellations.
Small nodes	Configure only replication capacity that is actually used. Even a small topology needs bounded timeouts and slot lifecycle; unlimited retention is not reliability.

Pigsty

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

Template	Effective value	Versus upstream boot	Source expression
OLTP	Unmodified	—	—
OLAP	Unmodified	—	—
CRIT	Unmodified	—	—
TINY	Unmodified	—	—

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG18–19 Beta 3 unmodified; OLAP: PG18–19 Beta 3 unmodified; CRIT: PG18–19 Beta 3 unmodified; TINY: PG18–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Changing it on the wrong primary, standby, sender, or subscriber role.
Watching only configured bytes/time instead of actual lag, slot position, and worker state.
Failing over to a node that lacks the old primary’s capacity or prerequisites.
Using infinite waits or WAL retention to hide a failed consumer.

max_logical_replication_workers · max_replication_slots · track_commit_timestamp · max_parallel_apply_workers_per_subscription · max_sync_workers_per_subscription · hot_standby