Patent ID: 7171465

Claim:
A method for use in each of two server computers to determine, when one of the server computers is restored from a fault, whether the server computer carried out a process most recently, applicable to a high availability computer system in which when one of the server computers executes the process and a fault occurs in the server computer, the other server computer takes over the process, each of the server computers having a storage unit, the method comprising the steps of: executing state-transition of the server computers when a fault occurs in one of the server computers or one of the server computers is restored from the fault, each of the server computers being constructed to assume four states, which are master state in which the server computer carries out the process and has a mate which takes over the process, single master state in which the server computer carries out the process and has no mate which takes over the process, slave state in which the server computer does not carry out the process but has information necessary for taking over of the process, and halt state in which the server computer does not carry out the process and holds no further information necessary for taking over of the process; storing a priority determined by the state-transition into the storage unit, the step of storing including the steps of: changing the priority of the server computer so as to indicate the highest priority when the state of the server computer is changed to the single master state; changing the priority of the server computer so as to indicate the second highest priority when the state of the server computer is changed to the master state; changing the priority of the server computer so as to indicate the lowest priority when the state of the server computer is changed to the slave state; and prohibiting a change of the priority of the server computer when the state of the server computer is changed to the halt state, determining, when the server computer is restored from the fault, whether the priority of the server computer is higher; determining whether the server computer carried out the process most recently, based on the result of determining whether the priority of the server computer is higher; and determining that the server computer becomes a server computer to take over the process, when it is determined that the server computer carried out the process most recently.