Implementing Database Replication Protocols based on O2PL in a Middleware Architecture

Database replication is a way to increase system performance and fault-tolerance of a given system. The price to pay is the effort needed to guarantee data consistency, and this is not an easy task. In this paper, we introduce a description of two 1-Copy-Serializable (1CS) [1] eager update everywhere replication protocols. The preliminary results of their implementation in the MADIS middleware architecture [2] are also presented. The advantage of these replication protocols is that they do not need to re-implement features that are provided by the underlying database. The first one does not rely on strong group communication primitives [3]; distributed deadlock is avoided by a deadlock prevention schema based on transaction priorities (whose information is totally local at each node). The second one manages replica consistency by the total order message delivery featured by Group Communication Systems (GCSs) [3].