PRIORITY ASSIGNMENT IN DISTRIBUTED REAL-TIME DATABASES USING OPTIMISTIC CONCURRENCY-CONTROL

In the studies of distributed real-time database systems (DRTDBS), it is always assumed that earliest deadline first (EDF) is employed as th e CPU scheduling algorithm. However, using purely (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 heu ristics have to be In the paper, the performance of different priority assignment heuristics for subtransactions in DRTDBS using optimistic concurrency control (OCC) protocol are investigated. It is found that purely deadline-driven heuristics. which suffice for distributed real- time systems, are not suitable for DRTDBS. On the other hand, the prop osed heuristic, which considers both deadline constraint and data cont ention, can give the best performance.