Concurrency control protocol for dynamic priority scheduling in hard real-time databases

Many real-time databases are used to support mission-critical applications, in which transactions have hard deadlines. The difficulties of providing a guarantee of meeting hard deadlines lie in the problems of priority inversion and deadlocks. Several priority ceiling protocols have been proposed to solve these two problems with fixed priority assignment using rate monotonic algorithm. In this paper, we develop a new concurrency control protocol MV-PL, which can be applied in dynamic priority scheduling so as to achieve higher processor utilization. Multiversion mechanism is adopted to increase the degree of concurrency and avoid unnecessary conflict blockings via dynamic adjustment of serialization order. And more locking conditions are defined so as to minimize unnecessary ceiling blockings existing in other protocols. It has also been proven that the new protocol have the single-blocking and deadlock-free properties. The simulation results show that the new protocol outperforms other protocols in terms of enhancing the schedulability of hard real-time transactions.