Priority Assignment for Sub-transaction in Distributed Real-time Databases

Recent studies on deadline assignment to sub-tasks in distributed real-time systems have suggested different heuristics for priority assignment to improve the system performance [6,10]. These heuristics only consider the real-time constraints of the tasks and may not be suitable for distributed real-time database systems (DRTDBS). In this paper, we examine the performance of these heuristics for DRTDBS and suggest better alternatives. Our performance results show that many factors, such as data conflict resolution, transaction aborts and restarts, that are unique to a database system in fact have significant impact on the performance of the heuristics for subtransaction priority assignment. One of our proposed heuristics, which considers both real-time constraints of the transactions and the impact on data contention, gives the best performance.