Adaptive co-scheduling for periodic application and update transactions in real-time database systems

In this paper, we study the co-scheduling problem of periodic application transactions and update transactions in real-time database systems for surveillance of critical events. To perform the surveillance functions effectively, it is important to meet the deadlines of the application transactions while maintaining the quality of the real-time data objects accessed by them. Unfortunately, these two goals are conflicting and difficult to be achieved at the same time. To address the co-scheduling problem, we propose a real-time coscheduling algorithm, called Adaptive Earliest Deadline First Co-Scheduling (AEDF-Co) in which we adopt a dynamic scheduling approach to adaptively schedule the update and application jobs based on their deadlines. The performance goal of AEDF-Co is that for given sets of periodic application and update transactions, it determines a schedule such that the deadline constraints of all the application transactions are satisfied and at the same time the quality of data (QoD) of the real-time data objects are maximized. Extensive simulation experiments are performed to evaluate the performance of AEDF-Co. The results show that by adaptively adjusting the release times of update jobs and scheduling the update and application jobs dynamically based on their urgencies, AEDF-Co is effective in achieving the performance goals and maximizing the overall system performance.