We are getting Arc Off-Line markings when looking at trend (depending on the time-scale) without actually having gaps in our archives.When exploring Google and PI-Tech support ... we came up with the "MarkArchiveGaps" tuning parameter as a possible solution.
However we seem to be getting into: "looking for a fix on some consequence of the previous fix".
So this is the track we are on:
- In order to lessen the load in the "OPC Source – Intf Node" we mostly use Advise Tag’s instead of Polling
- In order to get decent transitions for Points which have not changed for a long time we activated the /TA (Trend Advise) parameter.
- Now we get Arc Off-Line messages when looking at trends (depending on the time-scale) even though there are no actual gaps. (Apparently Compmax gets ignored when using /TA. This results in a very low event rate for some tags. Our archives cover +/- 3 days worth, Tag changes could take longer to update)
Is changing MarkArchiveGaps to 2 the next step? Or should we get bigger archives to solve this issue?
What are the consequences and Pro/Con’s for both these options?
What will be showing on the trends instead of Arc Off-Line (preferably the previous value, aka the first value found when going back as far as needed)?
Has anyone run into this scenario?
We would like to know the consequences beforehand this time :-).
Screenshot of situation where data is "found"
Screenshot of situation where data is "marked: Arc Off-line"