# primary_slot_name

> primary_slot_name sets the name of the replication slot to use on the sending server. It is a sighup setting present in PG12–18; the latest recorded boot default is empty.
---

> [!NOTE]
> **Fact — official short description:** “Sets the name of the replication slot to use on the sending server.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `string` | 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 | `""` | empty string |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG12 |
| Present in | PG12–19 Beta 3 |
| Removed in | No |
| Introduction commit | [`2dedf4d9a899`](https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=2dedf4d9a899b36d1a8ed29be5efbd1b31a8fe85) — Integrate recovery.conf into postgresql.conf |
| Commit date | 2018-11-25 |
| Discussion | [thread 1](https://www.postgresql.org/message-id/flat/607741529606767@web3g.yandex.ru/) |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG12–19 Beta 3 | `""` | — | empty string |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

Sets the name of the replication slot to use on the sending server. A configuration reload applies a new value; existing work already in flight is not retroactively changed.

The receiver names an existing upstream physical slot so the sender retains WAL needed by this standby. It improves continuity across disconnects but transfers disk-retention risk to the primary and must match slot lifecycle during failover.

Monitor and change primary_slot_name together with wal_keep_segments, wal_keep_size, wal_segment_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 primary_slot_name 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: PG12–19 Beta 3 unmodified; OLAP: PG12–19 Beta 3 unmodified; CRIT: PG12–19 Beta 3 unmodified; TINY: PG12–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Creating a slot without monitoring restart_lsn and primary disk usage.
- Dropping or reusing the slot during failover without proving consumer position.
- Assuming a slot alone archives or backs up WAL.
- 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.

## Related parameters {#related-parameters}

[`wal_keep_segments`](/parameters/wal-keep-segments/) · [`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/) · [`idle_replication_slot_timeout`](/parameters/idle-replication-slot-timeout/)

## References {#references}

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