A hierarchical precedence concurrency control protocol for high data contention database environments

In this paper, we propose a family of concurrency control protocols, called the Hierarchical Precedence Concurrency Control (HPCC) protocols, for high data contention database environments. HPCC attempts to be more aggressive by permitting more serializable schedules than the two-phase locking (2PL). It maintains cycle-free precedence hierarchies for conflicting transactions. Conflicting operations are allowed to proceed only if the hierarchical orderings of precedence is not violated. Transactions commit based on the serialization order established during the executions. A detailed simulation model has been implemented and extensive experiments have been conducted to evaluate the performance of the proposed approach. The results demonstrate that the proposed algorithm outperforms the two-phase locking over a wide range of system workloads.