Analytic modelling of locking protocols in database systems

The consistency of the database for concurrent transaction processing in database systems is guaranteed by concurrency control protocols which are normally implemented by two phase locking. Queuing network models are used to study two important locking protocols namely, the static and dynamic two phase locking protocols. Using simple combinatorial arguments and elementary probability theory, an efficient way of deriving expressions is provided for quantities such as the blocking delays of transactions, the probability of a lock being granted and the probability of deadlocks. Mean value analysis is then applied to the two models. The analysis is straightforward and the models are easy to understand. The analytic results show remarkable good agreement with simulation results. Some conclusions are drawn regarding the performance of locking protocols in the database systems