# wal_keep_segments

> wal_keep_segments — Sets the number of WAL files held for standby servers. Observed in PG9.0–12; its last measured boot default is 0 in PG12, with sighup context. It was removed in PG13.
---

> [!NOTE]
> **Fact — official short description:** “Sets the number of WAL files held for standby servers.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `integer` | Upstream pg_settings type |
| Context | `sighup` | Takes effect after configuration reload |
| Unit | — | Raw unit |
| Range | `0` – `2147483647` | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Replication / Sending Servers | Upstream classification |
| Latest boot value | `0` | 0 |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG9.0 (research boundary) |
| Present in | PG9.0–12 |
| Removed in | PG13 |
| Introduction commit | Not asserted: predates the PG9.0 research boundary |
| Commit date | — |
| Discussion | — |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG9.0–12 | `0` | — | 0 |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

Sets the number of WAL files held for standby servers. The parameter still exists in PG12 and is no longer recognized from PG13. PostgreSQL 13 replaced the segment-count interface with wal_keep_size, which expresses the retention floor in bytes rather than assuming a segment size.

This retained at least a count of old WAL segments for lagging standbys, so its byte effect changed with wal_segment_size. It was only a floor—not protection from every retention/removal condition—and PostgreSQL 13 replaced it with wal_keep_size.

Before upgrading, inspect wal_keep_size, wal_segment_size, max_slot_wal_keep_size, remove the old name from configuration, ALTER SYSTEM, role/database settings, and automation templates, and verify the replacement before starting PG13 or later.

## Tuning advice {#tuning-advice}

> [!TIP]
> **Advice.** These are workload-specific starting points and must be validated with measurements.

| Workload | Guidance |
| --- | --- |
| OLTP | Do not tune or continue emitting wal_keep_segments on PG13+. PostgreSQL 13 replaced the segment-count interface with wal_keep_size, which expresses the retention floor in bytes rather than assuming a segment size. Scan every configuration layer and regression-test the application before upgrade. |
| OLAP | Use the same migration path as OLTP, and also verify long batches, standbys, or large-object/extension workflows; removal of the old switch does not promise identical legacy behavior. |
| Small nodes | Delete the obsolete setting and adopt the supported replacement directly; do not emulate legacy behavior in scripts without a demonstrated compatibility requirement. |
{.full-width}

## Pigsty {#pigsty}

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG12; 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: PG9.0–12 unmodified; OLAP: PG9.0–12 unmodified; CRIT: PG9.0–12 unmodified; TINY: PG9.0–12 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Copying the old integer directly to wal_keep_size without multiplying by wal_segment_size.
- Treating the retained count as a maximum rather than a minimum floor.
- Leaving the removed name in PG13+ automation.
- Continuing to emit unknown parameter wal_keep_segments on PG13+.
- Deleting only the setting name without migrating dependent application behavior.

## Related parameters {#related-parameters}

[`wal_keep_size`](/parameters/wal-keep-size/) · [`wal_segment_size`](/parameters/wal-segment-size/) · [`max_slot_wal_keep_size`](/parameters/max-slot-wal-keep-size/) · [`max_wal_size`](/parameters/max-wal-size/) · [`primary_slot_name`](/parameters/primary-slot-name/) · [`idle_replication_slot_timeout`](/parameters/idle-replication-slot-timeout/)

## References {#references}

- [PostgreSQL 12 — wal_keep_segments](https://www.postgresql.org/docs/12/runtime-config-replication.html#GUC-WAL-KEEP-SEGMENTS)
- [Machine-readable GUC export](/data/guc.jsonl)