Reserve and release of a target device is managed using access permission IDs issued to a privileged device, such as a host computer. A second storage device, as the target device, is able to be shared by multiple first storage devices using the access permission IDs issued by the target device. The target device manages an access permission ID for use in identifying the access permission of other devices for accessing the target device. The target device executes processing to give as access permission to the privileged device that requests the access permission, and the target device judges whether to give access permission for access requests received after this, such as access requests from the first storage devices, according to the access permission ID originally supplied to the privileged device.