A Formal Analysis of the Deferred Update Technique

Introduction. In the deferred update technique for database replication, a number of database replicas are used to implement a single serializable database interface. Its main idea consists in executing all operations of a transaction initially on a single database replica. Transactions that do not change the database state can commit locally to the replica they executed, but other transactions must be globally certified and, if committed, have their update operations submitted to all replicas. Despite its wide use, we are not aware of any work that explored the inherent limitations and characteristics of deferred update database replication, ours being the first attempt in this direction. We specify a general abstract deferred update algorithm that embraces all the protocols we know of. This general specification allows for a better understanding of the technique, including its requirements and limitations and can be used to ease designing and proving specific protocols.