Performance analysis of two-phase locking

A straightforward analytic solution method is developed which takes into account the variability of transaction size (the number of lock requests). The authors first obtain analytic expressions for the probability of lock conflict, probability of deadlock, and the waiting time per lock conflict. They then develop a family of noniterative analytic solutions to evaluate the overall system performance by considering the expansion in transaction response time due to transaction blocking. The accuracy of these solutions is verified by validation against simulation results. Also introduced is a new measure for the degree of lock contention, which is a product of the mean number of lock conflicts per transaction and the mean waiting time per lock conflict (when blocked by an active transaction). It is shown that the variability in transaction size results in an increase in both measures as compared to fixed-size transactions of comparable size. The authors also provide a solution method for the case when the processing times of transaction steps are different