移动复制数据库系统冲突检测及消解策略

复制技术是提高移动库系统性能的一项关键技术，该文提出了一种新的移动复制数据库系统模型－事务级吉果集传递（TLRSP）移动复制模型，重点分析了该模型中的冲突检测及消解策略，并给出具体的实现算法，TLRSP移动复制模型允许移动用户在系统断连时存取数据库的本地副本并提交事务，重新连接时进行冲突的检测及消解，同时进行事务结果集的合并，最后通过增量刷新的方式进行同步处理，使得系统最终收敛于一致性的状态。此外，通过引入简化的事务日志，数据牌本号以及权限控制等概念，TLRSP模型有效地降低了移动数据库系统的资源消耗，保证了数据库的一致性，从而为移动数据库系统复制提供了一个可行的解决方案。

Conflict Detection and Resolution Strategy in Replicated Mobile Database Systems

Replication is one of the key techniques in promoting the performance of mobile database systems. A lot of research has been focused on mobile database replication recently, and many models and algorithms have been proposed. However, most of the work does not focus on the conflict reconciliation problem. Some approaches that do focus on the conflict resolution require specialized knowledge of the system for all transactions and special concurrency control models, which limits their adaptability. Besides, some proposed methods do not ensure transaction serialize ability, which can cause serious consistency problems in many circumstances. In order to solve these problems, a new mobile database replication scheme, Transaction Level Result Set Propagation (TLRSP) model, is put forward in this paper. The conflict detection and resolution strategy of TLRSP model is discussed in detail, and the implementation algorithm is proposed. In TLRSP model, mobile users are allowed to access local replicas of the database and locally commit mobile transactions when the system is disconnected. The locally committed transactions are sent to the fixed database server for conflict reconciliation and result set incorporation when the system is reconnected. In order to ensure database consistency, transactions locally committed at mobile hosts need to be validated at the database server before they can be globally committed. Therefore, mobile transactions that have executed conflicting operations will be aborted, and only those mobile transactions that do not violate the consistency of the database system can be globally committed. TLRSP model uses an incremental refresh method, and only recently updated data need to be transmitted during the synchronization process. Besides, by utilizing a simplified log structure and by introducing version number and access control into the system, TLRSP model reduces the resource consumption and communication costs. To sum up, through an efficient conflict reconciliation and result set propagation strategy, TLRSP model provides a flexible and effective solution to the replication problem of mobile database systems.