Non-serializable executions in heterogeneous distributed database systems

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 local autonomy of the participating local database systems. The authors introduce a new correctness criterion fur HDBMSs, two-level serializability (2LSR), and show that it preserves database consistency in several HDBMS models. Further, they present a simple protocol for ensuring that schedules in an HDBMS environment are 2LSR. This protocol is easily implementable and does not violate the local autonomy of sites