PURPOSE: To eliminate the need of retrieving a lock list and to manage the trial of locks utilizing shared and exclusive locks by comparing a tried lock relating parameter with at least a part of the lock relating parameters constituted in a two-dimensional array.

CONSTITUTION: For the lock management method, a first key utilizes a cartesian tree to be an offset inside the file of the start of a lock range and a second key utilizes the length of the lock, that is a span, respectively. For instance, it is assumed that the locks of five ranges are appropriately limitedly permitted by the parameter. The lock 1 is the shared lock started from a byte 75 whose span is 20 bytes, the lock 2 is the shared lock started from the byte 85 whose span is 45 bytes and the lock 3 is the exclusive lock started from the byte 215 whose span is 35 bytes. Further, the lock 4 is the shared lock started from the byte 360 whose span is 150 bytes and the lock 5 is the shared lock started from the byte 420 whose span is 40 bytes.