Priority assignment in distributed real-time databases using optimistic concurrency control

In studies of distributed real-time database systems (DRTDBSs), it is always assumed that earliest deadline first (EDF) is employed as the CPU scheduling algorithm. However, purely using the (ultimate) deadline for priority assignment may not be suitable, because different kinds of transactions, such as global and local transactions, may exist in the system. To improve the performance, more sophisticated assignment heuristics have to be employed. In this paper, the performance of priority assignment heuristics for subtransactions in DRTDBSs using the optimistic concurrency control (OCC) protocol is investigated. It is found that purely deadline-driven heuristics, which suffice for other distributed real-time systems, are not suitable for DRTDBSs. On the other hand, the proposed heuristic, which considers both the deadline constraint and data contention, can give the best performance