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The author develops the concept of commutable transactions, where a user initiating a commutable transaction permits the system to commute (recorder) his transaction in relation to other concurrent transactions so that the transaction, in case it faces abortion due to conflict, can be salvaged without the user's intervention. The user specifies a limit to the commutability of his transaction. A new synchronization mechanism for distributed system, called time-pad, is developed which allows a user to express the commutability of his transaction and reduces the probability of its eventual rejection. The two-phase lock synchronization scheme and the timestamp synchronization scheme can be viewed as special cases of the time-pad synchronization scheme. It is a user-controlled synchronization mechanism which can be tuned to improve the performance of those distributed database systems where the communication delay is large and the probability of transaction conflict is high.