# 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 {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `enum` | Upstream pg_settings type |
| Context | `internal` | Internal/preset and not user-settable |
| Unit | — | Raw unit |
| Range | — | Raw limits in the last observed version |
| Enum values | `minimal`, `replica`, `logical` | — for non-enum types |
| Category | Preset Options | Upstream classification |
| Latest boot value | `replica` | replica |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG19 Beta 3 |
| Present in | PG19 Beta 3 |
| Removed in | No |
| Introduction commit | [`67c20979ce72`](https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=67c20979ce72b8c236622e5603f9775968ff501c) — Toggle logical decoding dynamically based on logical slot presence. |
| Commit date | 2025-12-23 |
| Discussion | [thread 1](https://postgr.es/m/CAD21AoCVLeLYq09pQPaWs+Jwdni5FuJ8v2jgq-u9_uFbcp6UbA@mail.gmail.com) |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG19 Beta 3 | `replica` | — | replica |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

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 {#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. |
{.full-width}

## Pigsty {#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 | — | — |
{.full-width}

> [!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 {#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.

## Related parameters {#related-parameters}

[`wal_level`](/parameters/wal-level/) · [`max_replication_slots`](/parameters/max-replication-slots/) · [`max_wal_senders`](/parameters/max-wal-senders/) · [`track_commit_timestamp`](/parameters/track-commit-timestamp/)

## References {#references}

- [PostgreSQL 19 Beta 3 — effective_wal_level](https://www.postgresql.org/docs/19/runtime-config-preset.html#GUC-EFFECTIVE-WAL-LEVEL)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)