## 31.10. Configuration Settings

Logical replication requires several configuration options to be set.

On the publisher side, `wal_level` must be set to `logical`, and `max_replication_slots` must be set to at least the number of subscriptions expected to connect, plus some reserve for table synchronization. And `max_wal_senders` should be set to at least the same as `max_replication_slots` plus the number of physical replicas that are connected at the same time.

`max_replication_slots` must also be set on the subscriber. It should be set to at least the number of subscriptions that will be added to the subscriber, plus some reserve for table synchronization. `max_logical_replication_workers` must be set to at least the number of subscriptions, again plus some reserve for the table synchronization. Additionally the `max_worker_processes` may need to be adjusted to accommodate for replication workers, at least (`max_logical_replication_workers` + `1`). Note that some extensions and parallel queries also take worker slots from `max_worker_processes`.