DEFERRED LOCKING WITH BUFFER VALIDATION ON DEMAND FOR CLIENT-SERVER DATABASE CONSISTENCY - DL

In client-server database management systems (DBMSs), inter-transactio n caching is an effective technique for improving the performance. How ever, inter-transaction caching requires a cache consistency maintenan ce (CCM) protocol to ensure that cached copies at clients are kept mut ually consistent. Such a protocol could be complex to implement and ex pensive to run, since several rounds of message exchange may be requir ed. In this paper, we propose a new CCM scheme based on the primary-co py locking algorithm. In the proposed scheme, a number of lock request s and a data-shipping request are combined into a single message packe t to reduce client-server interactions, which are known to be very cri tical to the performance of client-server DBMSs. We examine its perfor mance tradeoffs on the basis of a simulation model under a wide range of workloads. The performance results indicate that the proposed schem e improves the overall system throughput significantly over the cachin g two-phase locking and the optimistic two-phase locking scheme. Its h igher performance mainly results from its lower communication overhead and lower degree of transaction blocking ratio.