移动计算环境中实时嵌套事务并发控制协议的研究

提出了移动计算环境中多版本乐观并发控制协议(MultiversionOptimisticConcurrencyControl,MVOCC)处理移动实时嵌套事务.协议消除了只读事务和更新事务之间冲突,通过动态调整事务串行次序,避免不必要的事务重启动.只读事务在移动主机处理,只读事务的响应时间大大改善.事务有效性检查分两级局部有效性检查和全局有效性检查.局部有效性检查在移动主机进行.通过局部有效性检查的事务提交到服务器进行全局有效性检查.如此早地检测数据冲突,节省了处理和通信资源.通过模拟仿真,对协议进行了性能测试,并与OCC-TI-WAIT50和HP2PL协议进行了比较.实验结果表明该协议要优于其它协议.协议不但能有效地降低事务的重启动率和延误截止时间率,而且改善只读事物的响应时间.

Research of Concurrency Control Protocol for Real-Time Nested Transactions in Mobile Computing Environments

Multiversion optimistic concurrency control (MVOCC) protocol was presented for processing mobile real-time nested transactions The protocol can eliminate conflicts between read-only and update transactions and resolve data conflicts flexibly using dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Read-only transactions can be efficiently processed at MHs. Respond time of read-only transactions is greatly improved. Transaction validation is performed at two levels: local validation and global validation. Local validation of transactions is performed at MHs , and transactions that survive in local validation must be submitted to server for global validation. Such an early data conflict detect detection feature can save processing and communication resources. The MHs do not need to synchronize with each other and servers for data conflict detection. The protocol presented is compared with OCC-TI-WAIT50 and HP2PL by simulation experiments. The results of experiment show that the protocol performs better than other protocols. The protocol presented can not only effectively reduce the miss rate of transactions and the restart rate of transactions, but also significantly improve the response time of read-only transactions.