In this thesis, the performances of concurrency control methods in main memory database systems (MMDBS) were analysed. Static locking (SL), dynamic two phase locking(D2PL), and an optimistic scheme were selected to investigate their performances in MMDBS environment. To reduce the number of transaction restarts in optimistic scheme, we slightly modified the Pradel's validation scheme and used it as optimistic scheme.
The transaction response time was selected as major performance index. In addition, lock table management overhead for SL, lock table management overhead including deadlock detection for D2PL, and transaction restart overhead for optimistic scheme were calculated and compared. According to the results of this study, the average response time of locking method was found to be mainly affected by workload of systems. In locking method, when system workload was low, SL performs better than D2PL. However, when system workload was high, D2PL performs better than SL. When we compared locking with the optimistic scheme, the performance of the optimistic scheme was better then D2PL. The reason is that concurrency control information processing time of the optimistic scheme was less than that of D2PL.
