【摘要】 同步处理技术是保持复制的移动数据库系统一致性的一项关键技术,但现有的事务级同步处理算法存在着一定的局限性.为了克服这些缺陷,并增强其实用性,提出了一种新的移动数据库同步处理模型──基于双时间印的事务级同步(DTSTLS)模型.DTSTLS模型采用了一种三级复制体系结构,系统可以直接使用通用的数据库产品作为其数据库服务器,因此具有良好的可扩充性.作为一种异步的多主副本复制方法,DTSTLS模型允许移动计算机在断连的情况下存取本地副本,从而造成系统短暂的不一致,重新连接时进行冲突检测及同步处理,使系统重新收敛于一致性的状态.此外,通过一种独特的时间印处理策略,DTSTLS模型减少了通信代价,并降低了资源消耗.实验结果表明,DTSTLS模型提高了移动数据库系统的资源利用效率,保证了事务调度的可串行性和数据库的一致性.更多还原

【Abstract】 Synchronization is one of the key technologies in maintaining the consistency of replicated mobile database systems. A lot of research has been focused on transactional synchronization schemes in recent years and many models and algorithms have been proposed. However, existing transactional synchronization schemes have some limitations. In order to solve these problems, a new synchronization scheme, double-timestamp transaction-level synchronization (DTSTLS) model, is put forward in this paper. DTSTLS model utilizes a three-tire architecture. Therefore existing database products can be used as its database server, which improves the flexibility and extensibility of the system. As an asynchronous group replication method, DTSTLS model allows mobile users to access local replicas of the database and to locally submit mobile transactions when the system is disconnected. The locally committed transactions are sent to the synchronization server for conflict reconciliation and synchronization when the system is reconnected. 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. In this way, the consistency of the database system is ensured. Besides, through a novel timestamp strategy, DTSTLS model cuts down the resource consumption and reduces the communication costs. Detailed simulation experiments are carried out, and the results show that the proposed methodology not only ensures the serializability and consistency of the mobile database system, but also reduces storage consumption and communication cost.更多还原