In FIG. 12, a process P such as an application, etc. operates in a user space, D is a device entry, the device driver 70 processes an input/output request from the process P, an OPEN process unit 71 performs a process associated with a start request (open) to use a decide (adapters A0 through An), a CLOSE process unit 72 performs a process associated with an termination request (close) to stop the