移动数据库中基于承诺排序的并发控制方法
A Concurrency Control Method Based on Commitment Ordering in Mobile Databases
摘要：
由于移动客户端的移动性，移动客户端与服务器的连接在不确定的时间和持续时间内断开，这是客户端-服务器模式下移动数据库并发控制面临的最大挑战。在移动数据库中应用悲观的并发控制的经典方法（如2 pl）会导致事务阻塞时间长，等待时间增加。由于移动数据库中事务中止率高，乐观方法不适用于移动数据库。在乐观并发控制方法的基础上，提出了OPCOT并发控制算法。减少移动客户端和服务器端之间的通信，降低事务的阻塞率和死锁，提高并发度是OPCOT算法采用乐观方法作为基础方法的最重要的动机。为了降低事务的流产率，在事务操作符的执行时间中为它们分配时间戳。除了检查调度器的提交排序属性外，在提交时间上分配的时间戳用于服务器。利用可串行化图证明了OPCOT算法调度器的可串行化性。仿真结果表明，与2 pl算法和乐观算法相比，OPCOT算法降低了事务的失败率和等待时间。
英文摘要：
Disconnection of mobile clients from server, in an unclear time and for an unknown duration, due to mobility of mobile clients, is the most important challenges for concurrency control in mobile database with client-server model. Applying pessimistic common classic methods of concurrency control (like 2pl) in mobile database leads to long duration blocking and increasing waiting time of transactions. Because of high rate of aborting transactions, optimistic methods aren`t appropriate in mobile database. In this article, OPCOT concurrency control algorithm is introduced based on optimistic concurrency control method. Reducing communications between mobile client and server, decreasing blocking rate and deadlock of transactions, and increasing concurrency degree are the most important motivation of using optimistic method as the basis method of OPCOT algorithm. To reduce abortion rate of transactions, in execution time of transactions` operators a timestamp is assigned to them. In other to checking commitment ordering property of scheduler, the assigned timestamp is used in server on time of commitment. In this article, serializability of OPCOT algorithm scheduler has been proved by using serializability graph. Results of evaluating simulation show that OPCOT algorithm decreases abortion rate and waiting time of transactions in compare to 2pl and optimistic algorithms.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
