On using similarity for resolving conflicts at commit in mixed distributed real-time databases

In a distributed real-time database system (DRTDBS), transaction atomicity is ensured by commit protocol. If data conflict occurs between executing and committing transactions, system's performance will be affected. In this paper, based on the deadline driven conflict resolution (DDCR) approach proposed by Lam et al. (1997), we propose an enhancement called the DDCR with similarity (DDCR-S), to resolve the executing-committing conflicts in a DRTDBS with mixed requirements of criticality and consistency transactions. In the DDCR-S, conflicts involving transactions with looser consistency requirement, the notion of similarity is adopted so that a higher degree of concurrency can be achieved and at the same time the consistency requirements of the transactions can still be met. Simulation experiments have been performed and the results have shown that the use of DDCR-S can significantly improve the overall system performance.