pg_create_physical_replication_slot(slot_name name [, immediately_reserve boolean ])
Creates a new physical replication slot named slot_name. The optional second parameter, when true, specifies that the LSN for this replication slot be reserved immediately; otherwise the LSN is reserved on first connection from a streaming replication client. Streaming changes from a physical slot is only possible with the streaming-replication protocol — see Section 51.3. This function corresponds to the replication protocol command CREATE_REPLICATION_SLOT ... PHYSICAL.