1 介紹
推動數(shù)據(jù)庫系統(tǒng)發(fā)展的一個主要因素是，人們希望將一個企業(yè)的操作數(shù)據(jù)綜合起來并能提供對數(shù)據(jù)的受控訪問，經(jīng)管綜合和受控訪問意味著集中管理，但這并不是目的。實際上，計算機網(wǎng)絡的發(fā)展促進了分散式的作業(yè)模式。這種分散的方式反映了許多公司的組織結果：在邏輯上分成多個分公司，部門，項目等，而在體制上分為辦公室，車間，工廠，每一個單元都維護著自己的操作數(shù)據(jù)。數(shù)據(jù)的共享和數(shù)據(jù)訪問效率的提高以來與分布式數(shù)據(jù)庫系統(tǒng)的發(fā)展，分布式數(shù)據(jù)庫反映了上述組織結構，使得每個單元的數(shù)據(jù)都是可訪問的，并將最近的數(shù)據(jù)存放于最常用的位置。
分布式DBMS有助于結局信息孤島的問題，有時，數(shù)據(jù)庫被看做是孤立的，不可訪問的電子島，就像遙遠的島嶼一樣。這可能是由于地理分割，計算機體系結構不兼容或通信協(xié)議不兼容原因造成的。把數(shù)據(jù)庫綜合成一個邏輯整體可能會改變這種思考的方式。


1. INTRODUCTION
A major behind the development of database systems is the desire to integrate the operational data of an organization and to provide controlled access to the data. Although integration and controlled access may imply centralization, this is not the intention. In fact, the development of computer networks promotes a decentralized mode of work. This decentralized approach mirrors the organizational structure of many companies, which are logically distributed into divisions, departments, projects, and so on, and physically distributed into offices, plants, factories, where each nit maintains its own operational data. The shareability of the data and the efficiency of data access should be improved by the development of a distributed database system that reflects this organizational structure, makes the data in all units accessible, and stores data proximate to the location where it is most frequently used.