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. 1 Introduction Transactions in a distributed real-time database system (DRTDBS) have constraints on their completion times which are usually..

A real-time active database for high transaction loads and moderate deadlines

A large class of real-time database problems has very high transaction loads and moderate deadlines. Traditional approaches have not been designed to handle such problems. A model based on the use of encapsulated events and rule objects has been developed. The model describes an active, real-time, object-oriented, memory-resident database environment (REACT). A system based on the model has been designed and implemented. A concurrency control algorithm was developed that uses the extra information available from the object-oriented and active features of REACT to pre-process the database and speed up concurrency control. Analysis was done for both single and multiple processor systems. For multiprocessor analysis a simulator was developed to verify the performance of REACT on a multiprocessor system. Examples of all the features needed for an actual system are given along with examples of how REACT can be used to solve real-world control and monitoring problems. Algorithms have been developed to allow users to test that the properties termination, confluence, and observable determinism hold for a target REACT database