# wal_sender_delay

> wal_sender_delay — WAL sender sleep time between WAL replications. Observed in PG9.0–9.1; its last measured boot default is 1 s in PG9.1, with sighup context. It was removed in PG9.2.
---

> [!NOTE]
> **Fact — official short description:** “WAL sender sleep time between WAL replications.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `integer` | Upstream pg_settings type |
| Context | `sighup` | Takes effect after configuration reload |
| Unit | `ms` | Raw unit |
| Range | `1` – `10000` | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Replication / Master Server | Upstream classification |
| Latest boot value | `1000` | 1 s |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG9.0 (research boundary) |
| Present in | PG9.0–9.1 |
| Removed in | PG9.2 |
| 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 | `200` | `ms` | 200 ms |
| PG9.1 | `1000` | `ms` | 1 s |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

PostgreSQL describes wal_sender_delay as follows: “WAL sender sleep time between WAL replications.” A configuration reload applies the value to the server without a full restart. The atlas measures it in PG9.0–9.1; boot_val is the compiled or initialized baseline, not proof of a running cluster's effective setting.

Early WAL senders slept for this interval between attempts to ship more WAL. It disappeared after PostgreSQL 9.1 as sender wakeup and streaming behavior evolved; modern latency and liveness controls are wal_sender_timeout, wal_receiver_status_interval, and wal_receiver_timeout, not a polling delay.

Read it together with wal_sender_timeout, wal_receiver_status_interval, wal_receiver_timeout, max_wal_senders. 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 | Do not add this retired name to a current OLTP configuration. Translate its intent to the documented successor, test the migration under connection and write concurrency, and remove stale automation that still emits it. |
| OLAP | For an upgrade or analytical estate, inventory every generated configuration before cutover. Map the old control to its successor and compare plans, throughput, WAL, or logging behavior rather than assuming the old numeric value is portable. |
| Small nodes | Delete the obsolete override after recording why it existed. On a small node, prefer the successor's default until measurements justify a new value; an unknown startup parameter can otherwise stop the server. |
{.full-width}

## Pigsty {#pigsty}

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG9.1; 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: PG9.0–9.1 unmodified; OLAP: PG9.0–9.1 unmodified; CRIT: PG9.0–9.1 unmodified; TINY: PG9.0–9.1 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Treating the measured boot_val for wal_sender_delay as proof of the effective value on an initialized or managed cluster.
- Applying a change as though it were immediate while pg_settings reports sighup context.
- Changing this setting in isolation without checking the linked limits, observability, and rollback path.
- Copying the removed name into a modern postgresql.conf instead of migrating to its documented successor.

## Related parameters {#related-parameters}

[`wal_sender_timeout`](/parameters/wal-sender-timeout/) · [`wal_receiver_status_interval`](/parameters/wal-receiver-status-interval/) · [`wal_receiver_timeout`](/parameters/wal-receiver-timeout/) · [`max_wal_senders`](/parameters/max-wal-senders/)

## References {#references}

- [PostgreSQL 9.1 — wal_sender_delay](https://www.postgresql.org/docs/9.0/runtime-config-wal.html#GUC-WAL-SENDER-DELAY)
- [Machine-readable GUC export](/data/guc.jsonl)