ReplicationRestart requireddefault 10
max_wal_senders
Sets the maximum number of simultaneously running WAL sender processes.
How you change it
Restart required
Defaults and ranges on this page were read from pg_settings on live PostgreSQL 18.4. Treat older majors as needing their own check before you copy a value.
What this means
The maximum number of concurrent WAL sender processes -- one per connected streaming replica or base backup. It must be high enough to cover every standby plus headroom for base backups running at the same time.
When it matters
Set it to your number of standbys plus a couple of spare slots for backups.
| Default | 10 |
|---|---|
| Range | 0 – 262143 |
| Type | integer |
| Change scope | Restart required |
| Category | Replication |
Check the current value
SHOW max_wal_senders;Tradeoffs
- • Too low: a new replica or pg_basebackup fails to connect.
- • Each sender is lightweight, so modest headroom is cheap.
- • Coordinate with max_replication_slots if you use replication slots.