Abstract

In the real time database management systems the mechanism of concurrency control 2PL-high priority, by applying a sacrificing approach of the low-priority transaction during the competition with high priority transaction, not only waste the resources of the system but also decrease the system efficiency due to the increase of the transaction failure because of miss deadline. The survey is focusing on the weak points of this mechanism and presenting a new approach that by omitting the unnecessary restarts greatly improve the efficiency of the system. We also present a new approach for determining the transaction's priority to provide the possibility of more successful transaction. This approach will be more prominent especially when there is more competition among the transactions for locking the resources of the system. By modeling the behavior system in Markov model, this increase in efficiency of the system comparing to the 2PL-HP mechanism has been improved.

Key words: Real time databases, concurrency control, transaction priority, performance evaluation.