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 memory, which stores a plurality of instructions; and a processor executing the instructions, the processor, executing a first type of initialization processing in which a progress status of an initialization is notified to another device management apparatus when a processing of the initialization having a first value is executed to the device, the processing being equivalent to a processing unit of the initialization processing, executing a second type of initialization processing in which a progress status of an initialization is notified to the other device management apparatus when a processing of the initialization having a value greater than the first value is executed, the processing being for a predetermined number of processing units, monitoring at least one of a generation status of access to the device and an operation state of the device, and changing over between the first type of initialization processing and the second type of initialization processing based on a monitoring result of the monitoring.