Research On Dynamic Data Replication In Dameng Database System

Data replication is an important technology which is often used to improve the usability and dependability of distributed database system. Traditionally, Data objects are replicated in static way, their replication schemes are assigned by database administrator; the schemes are static and unaltered during the replication process unless they are changed by administrator. However, if the read-write patterns change dynamically, in unpredictable ways, a static replication scheme may lead to severe performance problem. So, dynamic data replication is a new subject of distributed database system.In this paper, we present a distributed algorithm for dynamic data replication of an object in a distributed database system. The algorithm dynamically adapts the replication scheme of an object to the pattern of read-write requests in the distributed database system. It works in the read-one-write-all context, which means a file read involves only one replica and the write update is propagated to all the replica; the read-write pattern during a time period is in most cases predictable based on the read-write pattern in the immediately preceding time periods.Referred to replication model of Microsoft SQL Server, our replication model has been developed as six parts including publisher, subscriber, publication, subscription, data item and data source. The introduction of PULL subscribing structure fulfills bidirectional replication between database and database which is started by subscriber.In addition, the usage of trigger can monitor the data changes in publisher's database, thus the problem of catching the data changes has been worked out. And with the popular XML techniques (creating and parsing), transmitting replication data among networks has been better resolved.