Replicated MDBs are quite safe to compact. However, if there's any chance of corruption, it is very common that after the compact, replicability will be lost. So, before any compact, be sure you synch with another replica, so that if your replica loses replicability during the compact, you'll know all the unique data in it has already been merged with another replica. It's still a problem/annoyance, but not nearly as bad as losing replicability on a replica that *hasn't* been synched!