Abstract: The object of the invention is to enable automatic recognition of a content of change of configuration at a host side when physical configuration change such as the expansion or reduction of a storage subsystem occurs. Coupling information with respect to the storage subsystems is provided to the host side, and when physical configuration change occurs, a notice that change of configuration has been executed and the content of change of configuration is notified from the storage subsystem side to the host side, based on which the coupling information is updated automatically. According to this method, the host can constantly recognize the current adequate logical configuration of one or more storage subsystems that the host accesses.