Concurrency control in mobile distributed real-time database systems

With the rapid advances in mobile computing technology, there is an increas ing demand for processing real-time transactions in a mobile environment. T his paper studies concurrency control problem in mobile distributed real-ti me database systems(MDRTDBS). Based on the High Priority Two Phase Locking (HP-2PL) scheme, we propose a distributed real-time locking protocol, calle d Distributed High Priority Two Phase Locking (DHP-2PL), for MDRTDBS. In th e protocol, the characteristics of a mobile computing system are considered in resolving lock conflicts. Two strategies are proposed to further improv e the system performance and to reduce the impact of mobile network on the performance of the DHP-2PL: (1) A transaction shipping approach is proposed to process transactions in a mobile environment by exploring the well-defi ned behavior of real-time transactions. (2) We explore the application sema ntics of real-time database applications by adopting the notion of similari ty in concurrency control to further reduce the number of transaction resta rts due to priority inversion, which could be very costly in a mobile netwo rk. A detailed simulation model of a MDRTDBS has been developed, and a seri es of simulation experiments have been conducted to evaluate the performanc e of the proposed approaches and the effectiveness of using similarity for concurrency control in MDRTDBS. (C) 2000 Elsevier Science Ltd. All rights r eserved.