Shared memory for unwritten WAL.
At a glance
| Property | Value |
|---|---|
| Parameter | wal_buffers |
| Category | WAL |
| Default | -1 |
| Value type | memory (kB/MB/GB) |
| Change scope | Restart required |
What it does
Amount of shared memory used for WAL not yet written to disk. -1 auto-sizes it to 1/32 of shared_buffers (capped at one WAL segment, 16MB).
How to apply a change
Requires a full server restart (postmaster context). Set it in postgresql.conf and restart PostgreSQL.
Inspect the current value and source with SHOW wal_buffers; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'wal_buffers';.
Tuning guidance
The auto value is fine for most. On very high write concurrency, explicitly setting 16MB-64MB can reduce WAL-write contention.