OPERATING METHOD OF TRANSACTION OBJECT OF STORAGE SYSTEM

PROBLEM TO BE SOLVED: To provide a method for operating a transaction object while maintaining the completeness of data at the time of a power source fault in a controller such as a disk array controller or the like. SOLUTION: The transaction object 10 is provided with a roll-forward log 12 for holding an operation item to be executed and a roll-back 14 for listing the already executed operation items. When the power source fault is generated, the controller judges whether the controller is to complete an operation by using the roll-forward log 12 or to cancel the operation by using the roll-back log 14 when power is restored. This method is actually provided with a simple sequence adjusted to a single instruction for clearing the roll-back log 14 for making the judgement and thus making the entire operation atomic to the power source fault.