Evaluation of a multiple version scheme for concurrency control

摘要

This paper presents a thorough investigation of all relevant properties of a multiple version scheme for concurrency control. It offers conflict-free scheduling for reader transactions thereby generally reducing resource contention. By using a trace-driven simulation model we explored the effective parallelism achievable in multi-user database systems and the number of occurring deadlocks as a complementary measure. The workload was represented by six real-life object reference strings of different applications running on databases which vary in size between 60 MB and 2.9 GB. To compare and valuate the outcome of our experiments we used known results for RX-, RAC- and optimistic synchronization protocols derived under the same conditions. Furthermore, version-dependent criteria and their influence on general database performance were considered. The results obtained underline the value of the multiple version concept for concurrency control; many criteria vote for its use in future database systems with highly concurrent transactions.