Research And Implementation Of SyncML Based Synchronization Techniques For Heterogeneous Databases

On the basis of comparison and analysis on many existing data synchronization protocols and technologies, this thesis researches various problems that may arise in the procedure of synchronization in heterogeneous database. On the premise of the full self-government to users and on the basis of current heterogeneous database synchronization systems based on SyncML Protocol, we put forward a series of strategies and approaches to improve existing system, ensuring the stability and reliability of synchronization middleware in heterogeneous database, increasing system performance, and meeting the requirements of applications those demand high data security. Finally we implement a secure, stable and efficient system which can accomplish data synchronization in major commercial DBMSs including Oracle, Sybase and SQL Server. The main contributions of this thesis are summarized as follows.First, in order to meet the demands of database synchronization applications those need to synchronize a large amount of data, we design the "synchronization state table" in server and client side respectively to record process information during each synchronization process, and then we implement the "horizontal division" technique, and present a data-sync-capacity adaptation strategy, so that the problem of low stability when synchronizing a large deal of data in database synchronization process is solved.Second, due to peak dynamic server overload or other unforeseen reasons, the on-going synchronization process may be halted. In order to solve the problem of resuming abnormal synchronization, we design the "resuming at the breakpoints" mechanism, and implement a highly effective exception handling method which can significantly improve the exception resumption efficiency of the original system.Third, in order to ensure the consistency of each data copy and to solve synchronization conflict better, we implement three strategies which can automatically solve conflicts based on the design of the "synchronization schedule" in server side, design a set of manual conflicts solving methods based on the design of the "conflict detection table" which is used to detect and record conflicts in server, and provide the flow chart of the complete algorithm. The consistency of each data copy is ensured through the user-configurable conflict-dealing module.Fourth, in order to solve the problem of data security in synchronization process, we combine SyncML protocol with XML encryption mechanisms, and implement encryption and decryption to SyncML messages using AES algorithm. Our system is much safer than existing systems and can meet the application requirements of high security.Finally, combining our design with software engineering, we implement a system which can accomplish data synchronization in major commercial DBMSs including Oracle, Sybase and SQL Server based on existing prototype system. We test the performance of key modules. Experimental results validate that our system can stably and reliably synchronize data in heterogeneous database systems meanwhile keeping the autonomy of client systems and the availability of data.