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.