MS SQL Replication is a technology that allows a mirror copy of a database to be placed on a different server and automatically updated. Replication is normally bi-directional – i.e. changes made to one database are sent to the other. Bi-directional replication introduces the possibility of conflicts, when changes are made to the same piece of information on both servers at the same time. Handling conflicts can be complex, and normally requires special programming.

MS SQL Replication is an extremely useful technology: it can be used to efficiently share information between distributed offices; to support redundancy and disaster-recovery planning; and to make systems faster by locating copies of information closer to users.