ECS-DBMS中的更新传播技术及其测试与分析

Some Updated Data Transmitting Straregies for the Server of ECS-DBMS

在标准的Client/Server结构中 ,数据库处理由Server来承担 ,Client运行用户接口程序 ,直接和用户交互 ,并向Server发送数据库请求。而在增强型Client/Server结构的DBMS(简写为ECS DBMS)中 ,充分利用了可以利用的Client资源 ,包括长久存储器。对于数据库中经常使用数据 ,客户机可以将这些数据拷贝并存储到自己的磁盘中 ,以免下次使用这些数据时再去访问Server。另外 ,客户机的磁盘中 ,还可以存储该客户自己的专用数据 ,这样便可以提高系统的性能。由于公共数据都存放在Server中 ,数据一致性的维护也由Server来承担。当Server中出现更新时 ,Server要将更新的内容传递给需要该更新的Clients,以替换客户机磁盘中的旧数据。针对ECS DBMS ,介绍并提出几种Server更新传播策略 。

In the enhanced client/server structure ECS DBMS the client resoutce including perpetual memory is utilized fully. Both the frequently used data in the server and the client's own data can be stored in client's local disk,thus the client could avoid looking for the data in the server repeatedly. When some server tables are updated, there are many clients which need the updated data to take the place of the old data in the local disk. This prolblem is studied and some server transmitting strategies are proposed in this paper. These strategies are also simulated via computer software to test their performance.