In reference, update, and insertion processing, the lock of an un-transferred object is released, and then the lock of a transferred object is set when the pointer is traced for transfer between objects to thereby improve the parallel execution capability of the reference, update, and insertion. At that time, the IS-mode (in the case of reference processing) or the IX-mode (in the case of update and insertion processing) is set at the starting of the processing, and the lock is released at the time of completion of the processing. Furthermore, in deletion processing, after the pointer to a deletion target is separated or replaced and all the processing that acquires the lock of an object group has been completed, the region of the deletion target object is released.