In this thesis, the performances of two representative concurrency control methods for nested transactions, namely, Extended Two-Phase Locking(E2PL) and Multiple-Version Timestamp Ordering (MVTO), were compared using simulation approach. Based on the simulation results, in general, MVTO outperforms E2PL with respect to average response time, since the overhead induced by the inheritance of locks and by deadlocks is heavy in E2PL. When the frequency of conflicts is high, however, E2PL outperforms MVTO since the restart overhead in MVTO is heavy.