移动数据库缓存模型研究

针对移动数据库系统性能有待提高的问题，提出了一种移动数据库缓存模型。采用基于消息摘要的同步算法，通过比较移动客户端与服务器消息摘要表中的消息摘要值，完成缓存同步，维护移动客户端缓存与服务器数据的一致性；该模型还考虑了数据的时效性与事务的优先级，设计了一种基于价值函数的缓存替换算法。实验结果表明，随着缓存数据个数的增加，所提算法的缓存命中率高于最近最少使用(LRU)和LA2U算法，同时随着访问频率的增加，事务的重启率低于LRU和LA2U，有效提高了移动数据库缓存的性能。

Research on cache model in mobile database

To improve the performance of mobile database system, a cache model was proposed for mobile database. A kind of synchronization algorithm based on message digest was used in this model. By comparing the value of message digest in mobile client and server, the algorithm completed the cache synchronization, and maintained the consistency of mobile client cache and the data in server. The timeliness of the data and the priority of the transaction were considered in this model. A cache replacement algorithm based on cost function was designed. The experimental results show that the cache hit rate of the proposed algorithm is higher than Least Recently Used (LRU) and Least Access-to-Update Ratio (LA2U) algorithm along with the increase of the number of cache data. At the same time, the restart rate of transaction is lower than LRU and LA2U while the frequency of access increases. The performance of the cache of mobile database is improved.