Prefetch concurrency for maintenance operations.
At a glance
| Property | Value |
|---|---|
| Parameter | maintenance_io_concurrency |
| Category | Asynchronous I/O |
| Default | 10 |
| Value type | boolean / enum / numeric |
| Change scope | Per-session (SET) |
What it does
Like effective_io_concurrency but for maintenance work such as VACUUM prefetching. Default 10.
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 maintenance_io_concurrency; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'maintenance_io_concurrency';.
Tuning guidance
Raise on fast storage to speed up vacuum/analyze I/O; lower if maintenance is starving foreground queries of I/O.