When a failure has occurred, the situation is dealt with promptly according to this invention. As triggered by detection of a failure in any specified processor package of a plurality of processor packages, a processor for the specified processor package is temporarily substituted with a processor for another processor package, as an assignment destination of ownership which is assigned to the processor for the specified processor package, instead of actually transferring the ownership, thereby making the transition to an ownership-substituted state; and as triggered by an event that the failure is no longer detected in the specified processor package, a processor for the other processor package cancels the ownership-substituted state.