Exam AZ-220 topic 1 question 5 discussion

Schedule jobs on multiple devices. Azure IoT Hub enables a number of building blocks like device twin properties and tags and direct methods. Typically, back-end apps enable device administrators and operators to update and interact with IoT devices in bulk and at a scheduled time. Jobs execute device twin updates and direct methods against a set of devices at a scheduled time. https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-jobs Looks like D may be the correct answer.

Ans is B. We use device twins JSON document to make changes in the device with the reporterd/desired properties. https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-device-twins

While it is possible to use a direct method to trigger an OTA update on devices that connect to an Azure IoT hub, it is not the recommended method. Direct methods are typically used for invoking a specific action on a device in real-time, and they can be useful for managing device settings or executing a specific function on a device. However, when it comes to performing OTA updates, using cloud-to-device messages is usually the more appropriate method. Cloud-to-device messages can be used to send firmware updates or other configuration changes to devices, and they can be scheduled to occur at specific times or intervals using Azure IoT Hub's Jobs feature. Therefore, the recommended method for performing an OTA update on devices that connect to an Azure IoT hub by using scheduled jobs is to use a cloud-to-device message. Option C is the correct answer.

You can use a direct method to initiate device management actions (such as reboot, factory reset, and firmware update) from a back-end app in the cloud. The device is responsible for: Handling the method request sent from IoT Hub. Initiating the corresponding device-specific action on the device. Providing status updates through reported properties to IoT Hub. https://learn.microsoft.com/en-us/training/modules/examine-device-management-concepts-methods/3-device-management-patterns Answer: D

Agree with D

Answer is D https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-node-node-schedule-jobs

D, see link https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-c2d-guidance said that targets for Cloud-to-device messages is 'Single device by deviceId.' so no way for C

The key item in the question is 'will connect'. Which means D is likely wrong, since it works directly on connected devices. On the other hand, C is right (many devices will connect, and decide when to read the messages...since the messages can be queued in each device's queue, and it won't matter if some are connected or not.

my vote is for "C. a cloud-to-device message". There is a key statement in the question about the devices being usually disconnected and connecting at scheduled time. In that case a direct-method will likely fail. A cloud to device message instead is queued and will be picked up by the device as soon as it connects to IoT Hub. https://docs.microsoft.com/en-us/azure/architecture/example-scenario/iot/cloud-to-device

D is the correct answer. No confusion.

The answer is B. "IoT Hub will use the device twin properties to transfer the configuration change request to the device and monitor the progress" https://docs.microsoft.com/en-us/learn/modules/automate-iot-devices-management-with-azure-iot-hub/3-firmware-update-mechanism There are not many differences between updating devices manually or through jobs.