W. Ni, S.V. Vrbsky, Q. Fang, and J. Zhang (USA)
adaptive broadcasting, concurrency control, mobile computing, real-time databases
A mobile real-time database system is both a real-time system and a database management system. The mobile characteristics of such a system add to the challenge of meeting real-time deadlines and maintaining the consistency of the database using concurrency control. In this work we study concurrency control strategies that use adaptive broadcasting, a widely accept data dissemination approach for mobile environments, in which data is broadcast on demand. We assume that data is stored at the server, but execution is distributed, as mobile clients process their transactions locally. We present a real-time Virtual Locks protocol, that uses a conservative locking strategy and recognizes the real-time priorities of transactions. We study the real-time OPT-WAIT and OPT-SACRIFICE protocols, which we modify for the mobile environment. Performance results show that these strategies can meet the database consistency and timing constraints of real-time databases, even in a mobile environment.
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