Priority Scheduling of Transactions in Distributed Real-Time Databases
Priority Scheduling of Transactions in Distributed Real-Time Databases
复制标题
分布式实时数据库中事务的优先级调度
作者：
V. Lee;K. Lam;B. Kao
事务调度是分布式实时数据库系统设计中的一个重要问题。事务调度由优先级调度和实时并发控制两部分组成。在以往的研究中，这些问题虽然相互之间有着非常密切的互动关系，但大多是单独研究的。在本文中，我们提出了新的优先级分配策略DRTDBS和研究其对两个典型的实时并发控制协议（RT-CCP），高优先级两阶段锁定（HP-2 PL）和乐观的并发控制与广播提交（OCC-BC）的影响。我们的性能测试结果表明，许多因素，如数据冲突解决，数据争用程度和事务重启，这是唯一的数据库系统，有显着的影响，进而影响性能的实时并发控制协议的政策的性能。OCC-BC比HP-2 PL更受优先级分配策略的影响，因为冲突检测较晚。在优先级分配策略的设计中，我们发现无论是单纯的截止日期驱动策略还是数据竞争驱动策略都不适合DRTDBS。我们提出的政策，混合方法（MM），它考虑了交易的及时性和数据争用，优于其他政策在广泛的系统参数设置。
One of the most important issues in the design of distributed real-time database system (DRTDBS) is transaction scheduling which consists of two parts: priority scheduling and real-time concurrency control. In the past studies, mostly, these issues are studied separately although they have a very close interaction with each other. In this paper, we propose new priority assignment policies for DRTDBS and study their impact on two typical real-time concurrency control protocols (RT-CCPs), High Priority Two Phase Locking (HP-2PL) and Optimistic Concurrency Control with Broadcast Commit (OCC-BC). Our performance results show that many factors, such as data conflict resolution, degree of data contention and transaction restarts, that are unique to database systems, have significant impact on the performance of the policies which in turn affect the performance of the real-time concurrency control protocols. OCC-BC is more affected by the priority assignment policies than HP-2PL owing to the late detection of conflict. In the design of priority assignment policies, we have found that neither the purely deadline driven policies nor data contention driven policies are suitable for DRTDBS. Our proposed policy, the Mixed Method (MM), which considers both transaction timeliness and data contention, outperforms other policies over a wide range of system parameter settings.