Patent ID: 8473464

Claim:
A data recovery method in a multitasking or multithreading environment, the method comprising: creating a log record by performing bit-by-bit logging with respect to a lowest level bitmap of a multilevel bitmap; recovering the lowest level bitmap using the log record; and correcting a higher level bitmap corresponding to the lowest level bitmap based on the recovered lowest level bitmap, wherein when a bit value at a predetermined position of a data image is updated so that a before log image and an after log image of the log record is created, the before log image is configured such that a bit value at a position of the before log image that is going to be updated comprises a different bit value than positions of the before log image that are not going to be updated, the after log image is configured such that a bit value at an updated position of the after log image comprises a different bit value than non-updated positions of the after log image, and the after log image is a bit negation of the before log image.