To notify plural host I/O control units of a requested I/O devices by means of a signal when an I/O device receives other I/O requests from one or more other I/O control units which shares the requested device by sharing one or more I/O control units and I/O devices.
An MIH(missing interruption handler) time-out period is varied by a prescribed extension increment. This extension increment is controlled by a new long busy interruption signal that is applied to each of requester OS(operating systems) A to E by a requested CU (I/O control unit) 521 which delays an I/O request. The long busy interruptions are added to the OS A to E in an MIH time-out period when the MIH time-out extension is already decided. When the time-out state of a threshold time-out period of the CU is generated before the present MIH time-out period of the OS is over, the MIH time-out periods of the OS A to R are set in the time-out states and can be extended.
RICHARD ANTHONY LIPPBERGER
LUIS RICARDO UUBANJOO
HARRY MAURICE UDENFRIEND
