A decomposition solution to the queueing network model of the centralized DBMS with static locking

Abstract

The effect of concurrency control methods on the performance of computer systems is analyzed in the context of a centralized database with a static lock request policy, i.e., database transactions should acquire all locks before their activation. In the lock conflict model the L locks required by each transaction are uniformly distributed over the N locks in the database. The computer system is modelled as a queueing network. Two scheduling policies for transaction activation are considered: FCFS with and without skip. In each case the scheduling overhead for scanning the blocked transactions is taken into account. The number of transactions to be scanned is limited by a window size parameter. The system is analyzed using a hierarchical decomposition method, where the highest level model yields the mean user response time. The results of the approximate solution are validated using a detailed simulation, which shows that the analysis based on no resampling of locks is quite accurate and outperforms the simplified analysis with resampling of locks in accuracy. The effect of varying the values of parameters such as transaction size, granularity of locking, scheduling discipline for transaction activation, scheduling overhead, and window size on system performance is investigated.