A Pelion Device Management device has two main workflows:
When a device is first turned on, it starts its on-boarding process. It registers with Device Management, which means it gets an entry in Device Directory and its status is
registered. As part of the registration process, the device sets its registration period, telling the service how often the device will renew its registration (re-registering shows the service that the device is still valid). This setting is up to you. For more information, see the registration information section.
A registered device can either remain registered or become deregistered. It remains registered so long as it re-registers within the period it defined in its on-boarding process. It can be deregistered either by actively deregistering, or by failing to re-register within the period (in which case, Device Management deregisters it).
It's important to understand that a device's successful re-registration doesn't indicate that the device was online without interruptions; it means the device managed to re-register within the re-registration period. If your device's period is 24 hours, it may well have been offline for 23 of those hours and you will not know that from its Device Management status.
Tip: If you are using your own bootstrap service, rather than the Device Management service, you can have your device call the Device Directory API with more statuses, such as "enrolling".