Strategies for resolving inter-class data conflicts in mixed real-time database systems

Although many efficient concurrency control protocols have been proposed for real-time database systems, they are mainly restricted for systems with a single type of real-time transactions or a mixed set of soft real-time and non-real-time transactions only. Their performance objective usually aims at the minimization of the number of missed deadlines of soft real-time transactions or to guarantee the deadline satisfaction of hard real-time transactions. So far, it is still lack of any good study on the design of concurrency control strategies for mixed real-time database systems (MRTDBS), which consist of both hard and soft real-time transactions, and together with non-real-time transactions. Due to the very different performance requirements of hard and soft real-time transactions, existing real-time concurrency control protocols may not be suitable to MRTDBS. In this paper, we propose strategies for resolving data conflicts between different types of transactions in an MRTDBS so that the performance requirements of each individual transaction type can be satisfied and, at the same time, the overall system performance can be improved. The performance of the proposed strategies is evaluated and compared with a real-time optimistic approach, which has been shown to give a better performance than the lock-based protocols for soft and firm real-time transactions.