Maintaining Database Consistency in Heterogeneous Distributed DatabaseSystems

The concept of serializability has been the traditionally accepted notion of correctness in database systems. However, in a heterogeneous distributed database system (HDBMS) environment, ensuring serializability is a difficult task mainly due to the desire of preserving the various participating local database systems. In this paper, we introduce a new correctness criterion for HDBMSs, two level serializability (2LSR). We identify restrictions under which 2LSR schedules preserve database consistency. Further, we present a simple protocol for ensuring schedules are 2LSR. This protocol is easily implementable and does not violate the local autonomy of sites.