# wal_receiver_create_temp_slot

> wal_receiver_create_temp_slot sets whether a WAL receiver should create a temporary replication slot if no permanent slot is configured. It is a sighup setting present in PG13–18; the latest recorded boot default is off.
---

> [!NOTE]
> **Fact — official short description:** “Sets whether a WAL receiver should create a temporary replication slot if no permanent slot is configured.”

## Identity {#identity}

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

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG13 |
| Present in | PG13–19 Beta 3 |
| Removed in | No |
| Introduction commit | [`329730827848`](https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=329730827848f61eb8d353d5addcbd885fa823da) — walreceiver uses a temporary replication slot by default |
| Commit date | 2020-01-14 |
| Discussion | [thread 1](https://www.postgresql.org/message-id/CA%2Bfd4k4dM0iEPLxyVyme2RAFsn8SUgrNtBJOu81YqTY4V%2BnqZA%40mail.gmail.com) |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG13–19 Beta 3 | `off` | — | off |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

Sets whether a WAL receiver should create a temporary replication slot if no permanent slot is configured. A configuration reload applies a new value; existing work already in flight is not retroactively changed.

If primary_slot_name is empty, the receiver can create a temporary upstream slot for the lifetime of its connection. That prevents removal during the connection but vanishes on disconnect, so it cannot guarantee catch-up across an outage.

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

## Tuning advice {#tuning-advice}

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

| Workload | Guidance |
| --- | --- |
| OLTP | Size wal_receiver_create_temp_slot 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. |
{.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: PG13–19 Beta 3 unmodified; OLAP: PG13–19 Beta 3 unmodified; CRIT: PG13–19 Beta 3 unmodified; TINY: PG13–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#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.

## Related parameters {#related-parameters}

[`primary_slot_name`](/parameters/primary-slot-name/) · [`max_replication_slots`](/parameters/max-replication-slots/) · [`max_slot_wal_keep_size`](/parameters/max-slot-wal-keep-size/) · [`wal_keep_size`](/parameters/wal-keep-size/) · [`hot_standby`](/parameters/hot-standby/) · [`hot_standby_feedback`](/parameters/hot-standby-feedback/)

## References {#references}

- [PostgreSQL 19 Beta 3 — wal_receiver_create_temp_slot](https://www.postgresql.org/docs/19/runtime-config-replication.html#GUC-WAL-RECEIVER-CREATE-TEMP-SLOT)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)