In addition to satisfying data consistency requirements as in conventional database systems, concurrency control in real-time database systems must also satisfy timing constraints, such as deadlines associated with transactions. Concurrency control for a real time database system can be studied from several different perspectives. This largely depends on how the system is specified in terms of data consistency requirements and timing constraints. The objective of this research is to investigate and propose concurrency control algorithms for real time database systems, that not only satisfy consistency requirements but also meet transaction timing constraints as much as possible, minimizing the percentage and average lateness of deadline-missing transactions.

This paper presents a uni-processor real-time scheduling algorithm called the Generic Utility Scheduling algorithm (which we will refer to simply as GUS). GUS solves an open real-time scheduling problem — scheduling application activities that have time constraints specified using arbitrarily shaped time/utility functions, and have mutual exclusion resource constraints. A time/utility function is a time constraint specification that describes an activ-ity’s utility to the system as a function of that activity’s completion time. Given such time and resource constraints, we consider the scheduling objective of maximizing the total utility that is accrued by the completion of all activities. Since this problem is N P-hard, GUS heuristically computes schedules with a polynomial-time cost of O(n 3) at each scheduling event, where n is the number of activities in the ready queue. We evaluate the performance of GUS through simulation and by an actual implementation on a real-time POSIX operating system. Our simulation studies and implementation measurements reveal that GUS performs close to, if not better than, the existing algorithms for the cases that they apply. Furthermore, we analytically establish several timeliness and non-timeliness properties of GUS. Index Terms Real-time scheduling, time/utility functions, utility accrual scheduling, resource depen dency, mutual exclusion, overload management, resource management

We study implementation aspects of how to design a framework to support negotiation of real-time applications on shared memory multiprocessors. A negotiator adapts resource requirements to maximize user-perceived utility for any given workload. The adaption is achieved by selecting the degree of parallelism, algorithm, and timing parameters, within levels determined by the developer. We propose and evaluate a new schedulability test for shared memory multiprocessors and a new negotiation algorithm. By running an implementation of a subset of our described framework, we have observed that the capability of accepting new tasks is increased. Acknowledgments I would like to express my gratitude to Dr. Jan Jonsson, my advisor, for his guidance and advice throughout the course of this thesis work. He also helped me by suggesting literature, "creating problems", and even solving "nitty-gritty" problems. His feedback improved this thesis significantly. Many people provided me with knowledge...