# Troubleshooting device fleet disconnects
<a name="ota-troubleshooting-fleet-disconnects"></a>

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Amazon IoT device fleet disconnects can happen for multiple reasons. This article explains how to diagnose a disconnect reason and how to handle disconnects caused by regular maintenance of Amazon IoT service or a throttling limit.

**To diagnose the disconnect reason**

You can check the [AWSIotLogsV2](https://docs.amazonaws.cn/iot/latest/developerguide/cloud-watch-logs.html) log group in [CloudWatch](https://docs.amazonaws.cn//iot/latest/developerguide/cwl-format.html) to identify the disconnect reason in the `disconnectReason` field of the log entry. 

You can also use Amazon IoT's [lifecycle events](https://docs.amazonaws.cn//iot/latest/developerguide/life-cycle-events.html) feature to identify the disconnect reason. If you’ve subscribed to [lifecycle's disconnect event](https://docs.amazonaws.cn//iot/latest/developerguide/life-cycle-events.html#connect-disconnect) (`$aws/events/presence/disconnected/clientId`), you’ll get a notification from Amazon IoT when the disconnect happens. You can identify the disconnect reason in the `disconnectReason` field of the notification. 

For more information, see [CloudWatch Amazon IoT log entries](https://docs.amazonaws.cn//iot/latest/developerguide/cwl-format.html) and [Lifecycle events](https://docs.amazonaws.cn//iot/latest/developerguide/life-cycle-events.html).

**To troubleshoot disconnects due to Amazon IoT service maintenance**

Disconnects caused by Amazon IoT's service maintenance are logged as `SERVER_INITIATED_DISCONNECT` in Amazon IoT's lifecycle event and CloudWatch. To handle these disconnects, adjust your client-side setup to make sure your devices can be automatically reconnected to the Amazon IoT platform. 

**To troubleshoot disconnects due to a throttling limit**

Disconnects caused by a throttling limit are logged as `THROTTLED` in Amazon IoT's lifecycle event and CloudWatch. To handle these disconnects, you can request [message broker limit increases](https://docs.amazonaws.cn//general/latest/gr/iot-core.html#message-broker-limits) as the device count grows. 

For more information, see [Amazon IoT Core Message Broker](https://docs.amazonaws.cn//general/latest/gr/iot-core.html#message-broker-limits).