Conditional Waiting High Priority Transactions Algorithm for Enhancing the Performance in Real Time Database System

Abstract

Scheduling is an important issue in the design of real time database systems; Transactions in real time systems must be scheduled in such a way that they can be completed before their deadlines, the scheduler assigns a priority to each transaction based on its deadline,we are particularly interested in conflicts that can lead to priority inversions. Priority inversion problem may occur due to the sharing of resources among transactions, which can cause unbound delay to high priority transaction; this delaying may result in the higher priority transactions missing their deadline. In this dissertation we proposed a new scheduling algorithm Conditional Waiting High Priority (CWHP). This algorithm it Comparing transaction priorities at the time of the conflict and it considered the waiting time for transaction that request the lock of resources as same as the remaining time for transaction that hold the data at conflict time. We have used a simulation model for the purpose of comparing the performance results of our algorithm with other existing algorithms that are using the most popular priority assignment schemes Earliest Deadline First (EDF) policy.

Keywords: Real Time, Scheduling, Firm Deadline, Priority inversion,transactions, Earliest Deadline First