Commitment ordering based distributed concurrency control for bridging single and multi version resources

Multi version (MV) based database systems allow queries (read-only transactions) to be executed without blocking updaters (read-write transactions), or being blocked by them. Such systems become more and more common. In a multi database environment, transactions may span several single version (SV) based database systems, as well as MV based ones. The database systems may implement various concurrency control techniques. It is required that a globally correct concurrency control is guaranteed. Commitment ordering (CO) is a serializability concept, that allows global serializability to be effectively achieved across multiple autonomous resource managers (RMs; e.g. database systems). The RMs may use different (any) concurrency control mechanisms. Generic distributed CO algorithms, which guarantee the 1SER property over multiple RMs with mixed, SV and MV resources are presented. It is shown, that CO is a necessary condition for guaranteeing 1SER over multiple autonomous RMs with mixed resources