log_disconnections — PostgreSQL configuration parameter

Causes session terminations to be logged.

At a glance

What it does

Causes session terminations to be logged. The log output provides information similar to log_connections, plus the duration of the session. Only superusers and users with the appropriate SET privilege can change this parameter at session start, and it cannot be changed at all within a session. The default is off.

(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 log_disconnections; or SELECT name, setting, unit, context, source FROM pg_settings WHERE name = 'log_disconnections';.

Tuning guidance

Tune this for observability versus log volume, not for raw performance. More verbose logging helps diagnose problems but costs disk and I/O; quieter logging saves space but hides detail. Pick a level your log pipeline can store and search, and raise verbosity temporarily when investigating an incident.

Reference

PostgreSQL documentation — log_disconnections.