Reports the size of the main shared memory area, rounded up to the nearest megabyte.
At a glance
| Property | Value |
|---|---|
| Parameter | shared_memory_size |
| Category | Preset Options |
| Default | (see documentation) |
| Value type | integer |
| Change scope | Per-session (SET) |
| Available in | PostgreSQL 15, 16, 17, 18, 19 (added in 15) |
What it does
Reports the size of the main shared memory area, rounded up to the nearest megabyte.
(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 shared_memory_size; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'shared_memory_size';.
Tuning guidance
This is a preset, read-only parameter: it reports a value fixed when PostgreSQL was built or the cluster was initialized, and cannot be tuned at runtime. Read it to verify the server’s build or cluster configuration (for example when matching a replica or debugging a compatibility issue); there is no setting to adjust.