Specifies the cutoff age (in transactions) that VACUUM should use to decide whether to trigger freezing of pages that have an older XID.
At a glance
| Property | Value |
|---|---|
| Parameter | vacuum_freeze_min_age |
| Category | Vacuuming |
| Default | 50 |
| Value type | integer |
| Change scope | Per-session (SET) |
| Available in | PostgreSQL 12, 13, 14, 15, 16, 17, 18, 19 (added in 12) |
What it does
Specifies the cutoff age (in transactions) that VACUUM should use to decide whether to trigger freezing of pages that have an older XID. The default is 50 million transactions. Although users can set this value anywhere from zero to one billion, VACUUM will silently limit the effective value to half the value of autovacuum_freeze_max_age, so that there is not an unreasonably short time between forced autovacuums. For more information see vacuum_for_wraparound.
(Description quoted from the official PostgreSQL documentation.)
How to apply a change
Can be set per session with SET, per role/database with ALTER ROLE/DATABASE ... SET, or globally in postgresql.conf.
Inspect the current value and source with SHOW vacuum_freeze_min_age; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'vacuum_freeze_min_age';.
Tuning guidance
Lower it to freeze tuples sooner (more freeze work, spread out); raise it to defer freezing and reduce churn on frequently-updated tables. Coordinate with vacuum_freeze_table_age to avoid wraparound surprises.