Many 2-tier C/S based information systems have a centralized DB to support their data storage. But when many years passed by,their centralized DBs accumulate a vast array of data,which slow down their queries and cram every bandwidth of their network.

• 很多两层C/S结构的信息系统都采用了集中式数据库为系统提供数据存储支持,经过长时间地运行,所积累的海量数据使查询速度和网络通信性能大大降低。