Performance of multiversion concurrency control algorithms in maintaining temporal consistency

The authors present a model of typical hard real-time applications and the concepts of age and dispersion of data accessed by the real-time transactions. These are used to evaluate the performance of a class of multiversion lock-based concurrency control algorithms in maintaining temporal consistency of data in a real-time shared-data environment. It is shown that it is easier for such a concurrency control algorithm to maintain temporal consistency of shared data when the conflicting transactions are close in the lengths of their periods. The conflict pattern of the transactions has a more significant effect on the temporal inconsistency of data than the load level of the system. It is also desirable to have the transactions´ periods within a small range. The best case was obtained when the faster transactions have higher utilizations. It was also shown that the use of the priority inheritance principle with the lock-based concurrency control algorithms can reduce transactions´ blocking times and the number of transactions that access temporally inconsistent data as well as the worst-case age and dispersion of data