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Tip

By design, the use of MQTT removes the requirement for periodic publishing of infrequently changing data whilst maintaining data integrity.

Each time an MQTT Client connects, a BIRTH message is published which contains all metrics with a current time stamp. After that initial BIRTH message, metric changes are published using DDATA messages. If there are no metric changes for a data point, the timestamp provided in the BIRTH message is a valid timestamp for that data point.


By default the MQTT messages from Transmission are sent only upon Value or Quality changes and there is no provision to resend a single Tag or Device level Tags at any tag(s) at an interval if the values have not changed. 

However, MQTT Transmission has control tags that allow you to request the Edge to perform either a Node or Full Transmission refresh. This forces the Edge Node(s) to disconnect and reconnect resulting in the sending of NDEATH, NBIRTH and DBIRTH messages for Edge Node(s). 

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