Concurrency Control And Commitment Processing Of Real-time Transactions In Mobile Computing Environments

Recent advances in wireless communication technology have made mobile information services a reality and people can get timely information using their personal digital assistants and notebook computers through wireless communication network. Many systems in mobile computing environment are time-critical, such as mobile real-time stock trading systems, mobile real-time electronic commerce systems and real-time information distributing systems, etc. However, owing to the inherent limitations of wireless communication network, such as low speed, limited bandwidth, frequent disconnection and unpredictability, traditional distributed real-time transaction processing can't support the real-time systems in mobile computing environment. Therefore, it is necessary to develop new transaction process mechanisms for real-time transactions in mobile computing environment.Correctness notion, concurrency control protocol, and solution of priority inversion are main issues of concurrency control in mobile real-time database. Based on two consideration: a transaction from a MH which disconnects with FH maybe result in chain of blocking, and to restart a transaction takes a much longer time and requires much higher overheads because of low bandwidth; a solution of priority inversion PIA-DT is presented which integrate PA with PI and reduce the probability of chain of blocking. Then a concurrency control protocol MRCCP based on epsilon serializability and PIA-DT is proposed. Finally A transaction shipping approach is proposed to process transactions in a mobile environment to reduce the impact of mobile network on the performance.The commitment protocols in distributed environment are not suitable for mobile real-time transaction. We give a new atomic commitment protocol TBACP which improves the performance of system. In TBACP, first, participants actively vote, and coordinator wait for the votes from participants; then participants wait for the decision of coordinator to abort or commit. We set a respective timer for coordinator and participant and the value of timer depends on the deadline of transaction and the network performance.