## 30.8. 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.

The subscriber also requires the `max_replication_slots` to be set. In this case it should be set to at least the number of subscriptions that will be added to the subscriber. `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`.