PURPOSE: To allow a system to operate efficiently by transferring information on the prediction of the releasing of a peripherl equipment to and from the peripheral controller of another system which shares the peripheral equipment.

CONSTITUTION: When a magnetic disk controller 1 tries to use a magnetic disk device 3 which is used in common to another magnetic disk controller 2 and already occupied, whether the occupied magnetic disk device 3 is released within a specific time or not is discriminated; when it is released within the specific time, the controller 1 starts processing for the magnetic disk device 3 at the releasing time and when not, a disconnection is made temporarily and the magnetatic disk device 3 is connected at need after the processing for another magnetic disk device to perform processing after confirming the releasing state. Thus, the system operates efficiently.