# vacuum_cost_page_miss

> vacuum_cost_page_miss — Vacuum cost for a page not found in the buffer cache. Observed in PG9.0–19 Beta 3; its last measured boot default is 2 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
---

> [!NOTE]
> **Fact — official short description:** “Vacuum cost for a page not found in the buffer cache.”

## Identity {#identity}

| Field | Value | Meaning |
| --- | --- | --- |
| Type | `integer` | Upstream pg_settings type |
| Context | `user` | Settable by an ordinary user |
| Unit | — | Raw unit |
| Range | `0` – `10000` | Raw limits in the last observed version |
| Enum values | — | — for non-enum types |
| Category | Vacuuming / Cost-Based Vacuum Delay | Upstream classification |
| Latest boot value | `2` | 2 |
{.fields meta="-"}

## Lifecycle {#lifecycle}

| Fact | Value |
| --- | --- |
| First observed | PG9.0 (research boundary) |
| Present in | PG9.0–19 Beta 3 |
| Removed in | No |
| Introduction commit | Not asserted: predates the PG9.0 research boundary |
| Commit date | — |
| Discussion | — |

## Default history {#default-history}

| Versions | Raw `boot_val` | Unit | Human value |
| --- | --- | --- | --- |
| PG9.0–13 | `10` | — | 10 |
| PG14–19 Beta 3 | `2` | — | 2 |
{.full-width caption="Measured PG9.0–19 Beta 3 boot defaults"}

## How it works {#mechanism}

Vacuum cost for a page not found in the buffer cache. It can be changed at session scope, so different sessions may observe different behavior.

VACUUM accumulates virtual cost for page hits, misses, and dirties; after the balance reaches vacuum_cost_limit it sleeps for vacuum_cost_delay and resets. This is coarse I/O pacing rather than an exact bandwidth cap, and the wraparound failsafe bypasses throttling.

Monitor and change vacuum_cost_page_miss together with vacuum_cost_delay, vacuum_cost_limit, vacuum_cost_page_hit. Validate on the relevant server role and real workload, then use its user 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 | Tune vacuum_cost_page_miss from autovacuum duration, dead-tuple growth, and foreground I/O latency together. Prefer per-table overrides for hotspots; global throttling must not let cleanup fall permanently behind. |
| OLAP | During post-load windows, a larger budget or shorter delay can improve maintenance throughput, but verify that scans do not starve queries/imports. Failsafe activation means normal pacing already failed. |
| Small nodes | Keep conservative defaults. On slow disks, lowering concurrency or overriding one table is usually more controllable than making the delay arbitrarily large. |
{.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: PG9.0–19 Beta 3 unmodified; OLAP: PG9.0–19 Beta 3 unmodified; CRIT: PG9.0–19 Beta 3 unmodified; TINY: PG9.0–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

## Common pitfalls {#common-pitfalls}

- Changing the global value while a table storage parameter overrides it.
- Treating reltuples and cumulative change statistics as exact real-time counts.
- Blaming a threshold without checking long transactions, replication slots, and worker saturation.
- Buying short-term quiet by deferring maintenance until wraparound failsafe activates.

## Related parameters {#related-parameters}

[`vacuum_cost_delay`](/parameters/vacuum-cost-delay/) · [`vacuum_cost_limit`](/parameters/vacuum-cost-limit/) · [`vacuum_cost_page_hit`](/parameters/vacuum-cost-page-hit/) · [`vacuum_cost_page_dirty`](/parameters/vacuum-cost-page-dirty/) · [`autovacuum_vacuum_cost_delay`](/parameters/autovacuum-vacuum-cost-delay/) · [`autovacuum_vacuum_cost_limit`](/parameters/autovacuum-vacuum-cost-limit/)

## References {#references}

- [PostgreSQL 19 Beta 3 — vacuum_cost_page_miss](https://www.postgresql.org/docs/19/runtime-config-vacuum.html#GUC-VACUUM-COST-PAGE-MISS)
- [PostgreSQL 19 release notes](https://www.postgresql.org/docs/19/release-19.html)
- [Machine-readable GUC export](/data/guc.jsonl)