Research On Data Consistancy In Dispersed Redundant Databases

With the development of computer technology and the deeper degree of enterprise informatization, many vocations, departments and institutions have realized the computerized management internally, information sharing between different departments becoming more and more frequent.But because different enterprises have their respective geographical positions and ways of informatization construction, there are much redundant data among the departments.It is the key point to know which method to adopt to guarantee the consistency of the redundant data on the process of enterprise informatization.This thesis proceeds from this practical problem.Firstly it overviews the Middleware technology, highlighting the research of JMS and showing its advantages in the dispersed information system. Later it analyzes XML, summarizing the crucial technology on usage. Finally it analyzes some main methods applied to maintain the data consistency, and based on this, it brings forward the model to maintain data consisitency between different redundant databases.This model is mainly to make use of the asynchronous information processing mechanism of JMS,adopting loosely-coupled mode between various enterprises' information systems.It uses XMLas middle data format with the assist of Weblogic server to store and intransit to meet the aim of dataconsisitency between different dispersed redundant data bases.With the help of virtual dispersed redundant databases in laboratory room, this thesis realizes many steps: applying trigger to distill the changing data in databases, using DOM to read the changing data into XML, making use of Weblogic as the server to transmit information, the sending and receiving of JMS information, the read-in of XML data into databases, etc.It has realized the various functions of the model and attained the expected effects. The design and realization of the model not only embodies JMS's platform universal property,and XML's characters of mode description disconcerning with platform, language and contract and data exchanging,etc. It also manifests that appling the two technology to maintaindispersed redundant databases is feasible, meanwhile, providing great references for the exploitation and integration of the enterprises information system.