The Research On The Data Consistency In Mobile Transaction Processing

In last ten years, the improvements and integration of computing technology and wireless communication made a new computing mode, mobile computing, become reality. Driven by the need of application and with the progress of hardware and corresponding software technology, mobile computing developes quickly and plays an important role in more fields. The research on database management in mobile environment, which is known as mobile computing, has become a new hot topic in database reseach society.Research mainly focuses on replication&caching, location management, query optimizing, data broadcast, security, mobile transaction processing and human-machine interface technologies. Among these topics research of mobile transaction processing is one of the key technologies.One of the most important missions of transaction processing is maintaining the data consistency. The wide differences between mobile computing environment and static distributed computing environment make the traditionary technology for this mission not suitable. Some more work needs to be done in this direction in order to accommodate the restrictions imposed by mobile environment.In this paper we first introduce the research status on mobile transaction processing, focusing on the progeny of mobile transaction model study. We also discuss the features of desirable model, then get a category of present models based on the degree of data consistency they support.Then we analyze the data consistency technology so far, and point out the unsolved problems. Based on the three-tier replication architecture (TTR), we select the consistency in replication and broadcasting as reseach focus.How to maintain the consistency of the whole replication system is an important problem of database replication. We present a variably consistent server replication mechanism, called VCSR. It grounds on the tranditional weakly consistent data replication technology. It supports the stong transaction concept, which enables user's variable consistency applications. For primary server may become the bottle of the whole system, VCSR uses a concurrency control protocol based on voting, which also trade-off the network overhead. In this mechanism, voting information and temporary transactions propogate through the whole system with a periodical pairs synchronization procedure, whick still maintain the convergence of the system and serializability of concurrent update transactions. Besides, VCSR decides the transaction processing manner based on the conflict probability of applications.Broadcasting must ensure the data broadcasted to the client are consistent. Unfortunately, most researches focus on the broadcast algorithms but neglect this precondition. We analyze the three kinds of consistency problems in mobile database with broadcasting. To solve these problems, we introduce a new concurrency control protocol, referred to as BAUO. Detail proof of its correctness and validation is presented.Finally, this thesis summarizes our main achievements and forecasts our work in the future. Regarding our research, we argue the work is worth of being put into practice.