In this paper, we propose a concurrency control protocol, called thePrudent-Precedence Concurrency Control (PPCC) protocol, for high datacontention database environments. PPCC is prudently more aggressive inpermitting more serializable schedules than two-phase locking. It maintains arestricted precedence among conflicting transactions and commits thetransactions according to the serialization order established in theexecutions. A detailed simulation model has been constructed and extensiveexperiments have been conducted to evaluate the performance of the proposedapproach. The results demonstrate that the proposed algorithm outperforms thetwo-phase locking and optimistic concurrency control in all ranges of systemworkload.
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