AF function PrevEvent() should return timestamp of previous event even if data is "No Data"
Normally AF function PrevEvent() returns the timestamp of the previous event for a specified timestamp.
But if the previous event is system digital state "No Data" it does not return the timestamp but again system digital state "No Data". That is not what one would expect.
PrevEvent works ok for other system digital states.
Performance equation function PrevEvent works as expected.
ADMIN RESPONSE
Aug 20, 2022
We investigated this some more and unfortunately changing this behavior would break backwards compatibility with existing applications. As a result, we will not be implementing this request.
Please confirm that this is a system digital state of "No Data" and not a user injected value of "No Data". Also please describe what is generating this value. Is it from an OSIsoft interface or some other software?
This feedback results from TechSupport Case #804783.
Actually it is really a system digital state "No Data". The values gets into PI via a batchfl interface.
Answer from developers regarding this matter:
The behavior for the No Data digital state in AF is the expected one according to the design. It was decided to process a ¨No Data¨ value as if there was not any value, instead of processing it as a value coming from a digital state for consistency with other possibilities.
BUT: wouldn't it be then consistent to ignore this "No data" entry and return the timestamp of the previous event (ignoring further "No Data" events). It would be ok to return "No Data" if no previous data (other than "No Data") would exist.
