1. A device management apparatus that executes an initialization processing to a device that stores user data in a background of access to the device, comprising: a first initialization processing section executing a first initialization processing in which a progress status of an initialization is notified to another device management apparatus every time the initialization equivalent to a processing unit of the initialization processing is executed to the device; a second initialization processing section executing a second initialization processing in which a progress status of an initialization is notified to the other device management apparatus every time the initialization for a predetermined number of processing units is executed to the device; a monitoring unit monitoring at least one of a generation status of access to the device and an operation state of the device; and a changeover section changing over the first initialization processing and the second initialization processing based on a monitoring result of the monitoring unit.