Force WAL/data changes to durable storage.
At a glance
| Property | Value |
|---|---|
| Parameter | fsync |
| Category | WAL |
| Default | on |
| Value type | boolean / enum / numeric |
| Change scope | Reload (no restart) |
What it does
When on, the server flushes data to disk so it survives an OS or hardware crash. Turning it off risks unrecoverable data corruption on a crash.
How to apply a change
Takes effect on configuration reload (sighup context). Run SELECT pg_reload_conf(); or send SIGHUP — no restart needed.
Inspect the current value and source with SHOW fsync; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'fsync';.
Tuning guidance
Never turn off in production. The only acceptable use is throwaway data or initial bulk loads you can restart from scratch.