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Historical Data of PI AF Attributes - Trend Visualization

Question asked by Lorenzo.vento on Oct 20, 2017
Latest reply on Oct 20, 2017 by Lorenzo.vento

Hi everybody


I have a question about the visualization of PI AF attributes, which are not linked to PI Tags, in a PB or Coresight Trend: Are historical data preserved?


I have the following situation:

- Attribute1     Linked to PITag1 (Data Reference: PI Point)

- Attribute2     Linked to PITag2 (Data Reference: PI Point)

I create now a third attribute with Data Reference Formula:

- Attribute3     Formula: Attribute1 OR Attribute2


When I put the attribute3 in a Trend I'm able to visualize historical data for the Attribute3, however this one is not connected to a PI Tag. Furthermore I can display historical data younger than the attribute3 itself. If I implement the same logic with an Analytics, historical data are not available (better said: always equal to the actual value).


I came to the conclusion, that using the Data Reference "Formula" the historical data are preserved also for simple attributes, but I'm little bit confused with this, as I can not understand, where Historical data are stored?


Does someone have experience about that and give me some explanation? Can you garante me, that using the Data Reference "Formula" the historical data are long-term preserved and corrected?


Thank you for your answer.

Best regards,