It is a problem which database deviser and developers concerning very much that how to regard a DBMS application system as a whole availably and to improve its running efficiency.

• 如何有效地将DBMS应用系统作为一个整体，提高其运行效率，是数据库应用系统设计开发人员十分关心的问题，它直接影响到用户的接受程度和整个系统的生命力，也是应用系统成功的关键因素之一。