effective_wal_level

effective_wal_level — Shows effective WAL level. Observed in PG19 Beta 3; its last measured boot default is replica in PG19 Beta 3, with internal context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.

Note

Fact — official short description: “Shows effective WAL level.”

Identity

Type , Valueenum: Upstream pg_settings type
Context , Valueinternal: Internal/preset and not user-settable
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Valueminimal, replica, logical: — for non-enum types
Category , ValuePreset Options: Upstream classification
Latest boot value , Valuereplica: replica

Lifecycle

Fact	Value
First observed	PG19 Beta 3
Present in	PG19 Beta 3
Removed in	No
Introduction commit	`67c20979ce72` — Toggle logical decoding dynamically based on logical slot presence.
Commit date	2025-12-23
Discussion	thread 1

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG19 Beta 3	`replica`	—	replica

How it works

PostgreSQL describes effective_wal_level as follows: “Shows effective WAL level.” It is read-only state reported by PostgreSQL, not an operator-controlled tuning knob. The atlas measures it in PG19 Beta 3; boot_val is the compiled or initialized baseline, not proof of a running cluster’s effective setting.

Unlike configured wal_level, this read-only value reports the operational logging level. PostgreSQL 19 can maintain logical-equivalent WAL when logical slots require it even if wal_level is replica, and a standby inherits the effective value from the most upstream server in its replication chain.

Read it together with wal_level, max_replication_slots, max_wal_senders, track_commit_timestamp. Check SHOW and pg_settings on the target server, verify the source and pending_restart fields, and compare workload, logs, and resource metrics before and after any change.

Tuning advice

Tip

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

Workload	Guidance
OLTP	Keep the upstream default until a reproducible operational need is demonstrated. Test under representative concurrency and inspect logs, latency, and the related settings before changing cluster-wide policy.
OLAP	Evaluate the setting with representative long-running and batch work. Measure total runtime, resource use, log volume, and failure behavior across the whole job rather than one isolated operation.
Small nodes	Minimize overrides and document rollback. A small system has less room for extra logging, workers, memory, or retained WAL, so validate the change with explicit resource limits.

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: PG19 Beta 3 unmodified; OLAP: PG19 Beta 3 unmodified; CRIT: PG19 Beta 3 unmodified; TINY: PG19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

Treating the measured boot_val for effective_wal_level as proof of the effective value on an initialized or managed cluster.
Applying a change as though it were immediate while pg_settings reports internal context.
Changing this setting in isolation without checking the linked limits, observability, and rollback path.
Depending on beta behavior in production without retesting the PostgreSQL 19 final release.

wal_level · max_replication_slots · max_wal_senders · track_commit_timestamp