Edge Historian - data pruning - 8.1.9

Edge Historian Not Storing Every Change

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I am attempting to analyze tag history at the edge for MQTT Engine tags to confirm peer to peer communications between edge nodes are operating as expected. I noticed large numbers of tag history entries missing from the Edge as compared to our central Ignition gateway and went down a bit of a rabbit hole with checking packet loss, TCP dumps etc... I then began querying the tag historian in the edge to see what was being stored, I noticed that as I queried, tags would be stored but then later removed as new values came in and I could see that the messages were being received by Engine consistently. Is this the intended functionality of the edge historian? Am I missing something? The tag history is configured as follows:

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With identical settings for the same tag in the central gateway which has no loss in the historian.

Note: this tag changes every minute and there are only 6 tags in engine which are being used for this test.

Both Edge and Central are using Ignition 8.1.9

Are you sure the deadband style is the same? When style is "analog" (or auto for floats), the historian algorithm is a good bit more complicated, and pacing of data through your gateway network could have an impact. Consider "discrete" style for more predicable storage behavior (but more data consumption).

You have deadband "off", so discrete is probably the correct style anyways.

Right, I misunderstood the 'deadband' settings originally. Thanks for pointing that out! I did double check and saw that the central gateway 'Deadband Style' is also set to analog. I have changed to discrete on the edge and it seems to be behaving more appropriately.