分布式数据库系统NHD^2B的网络数据字典

THE NETWORK DATA DICTIONARY OF NHD^2B SYSTEM

网络数据字典(NDD)是分布式数据库系统的重要组成部分。本文介绍了NHD^2B系统中网络数据字典的设计与实现。着重考虑了目录的分布问题:参照实际环境,我们对目录分布代价函数的一般表示进行了一定的修正,并比较了几种分布策略的代价,最终确定了NHD^2B中各种目录的分布方案。文中的推导结果对解决建立在广播网上的分布式数据库系统的目录分布问题具有重要的作用。

Network Data Dictionary(NDD)is an important component in adistributed database system.In this paper,the design and realization of the NDD in NHD B is discussed.The directory allocation problem is taken into particular account.According to thereal enviroment,the cost functions of directory system are revised,and severalallocation strategies are compared.Finally,the allocation strategies for differentkinds of directories are determined in NHD^2B.The conclusions deduced in this paper are of great uses in tackling the directoryallocation problem in a distributed database system on a broadcast network.