Abstract: MVOCC-DA-2LV(Multiversion optimistic concurrency control-dynamic adjustment of serialization order-two-phase validation) protocol is proposed for mobile broadcast environments. Mobile real-time transaction processing is performed in two stages. In the first stage transaction processing is performed at mobile host (MH), and in the second stage at database server (DBS). Transactions that survive in partial validation in MH must be submitted to DBS for final validation. Such an early data conflict detect detection feature can save processing and communication resources. The protocol can eliminate conflicts between mobile read-only and mobile update transactions, and resolve data conflicts flexibly using dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Respond time of mobile read-only transactions is greatly improved. The protocol presented is compared with PVTO and HP2PL by simulation experiments. The results of experiment show that the protocol performs better than other protocols.

Key words: two-phase validation, multiversion data broadcast, mobile real-time database systems, multiversion optimistic concurrency control, dynamic adjustment of serialization order

摘要： 提出了移动广播环境中MVOCC-DA-2PV(Multiversion Optimistic Concurrency Control with Dynamic Adjustment of serialization order using Two-Phase Validation) 并发控制协议。移动实时事务处理分两阶段进行。第一阶段在移动主机(mobile hosts，MHs)上处理，第二阶段在服务器上处理。移动主机(MHs) 上所有移动事务执行局部部分向后有效性确认，与在服务器提交事务进行有效性确认。如果移动事务通过MH上部分有效性确认，提交到服务器进行最终有效性确认。提交到服务器上进行有效性确认的移动事务还必须对服务器事务进行有效性确认，使用向前有效性确认方法。如此早地检测数据冲突，节省了处理和通信资源。协议消除了移动只读事务和移动更新事务的冲突，使用动态调整串行次序技术，避免了不必要的事务重启动。降低了移动只读事务的响应时间。通过模拟仿真，对MVOCC-DA-2PV协议进行了性能测试，并与PVTO和HP2PL进行了比较。实验结果表明MVOCC-DA-2PV并发控制协议要优于其它协议。

关键词: 两阶段有效性确认, 多版本数据广播, 移动实时数据库系统, 多版本乐观并发控制, 动态调整串行次序