基于MDRTDB并发控制协议DHP-2PL的研究

并发控制协议是确保数据库性能目标的一个关键问题,对移动分布式实时数据库(Mobile Distributed Real-time DataBase,简称MDRTDB)并发控制协议-分布式高优先级两段锁协议(Distributed High Priority two Phrase Locking protocol,简称DHP-2PL)从两个方面做出了改进:一是采用动态优先级分配策略,能够缩短实时事务执行的等待时间和避免饥饿现象的产生;二是为了增加并发度在加锁机制中使用混合加锁粒度,同时能够减少加锁开销。最后通过模拟应用环境的性能测试表明,这两方面的改进更好地满足了事务截止期的要求,提高了移动实时事务的成功率。

Research on concurrency control protocol DHP-2PL for Mobile Distributed Real-Time DataBase based

The concurrency control protocol is essential for achieving high performance.This paper studies the distributed high priority two phrase locking protocol(DHP-2PL) for mobile distributed real-time databases.Two strategies are proposed to further improve the system performance:on the one hand,a dynamic priority assignment policy is adopted,which can shorten the executive time of real-time transactions and avoid the "Hunger" phenomenon;on the other hand,in order to increase the level of concurrency control,a hybrid locking mechanism is proposed and it can reduce the locking expense.The performance is measured and analyzed in the end of the paper.It is shown that the improvement of two methods can satisfy the deadline demands of transactions and improve the successful ratios of mobile real-time transactions.