Delay Real-Time Calculations until backfill is finished.
For recursive Analyses such as below :
PrevVal(tagA,'*') + 'TagB' → output : tagA
When the PI Analysis Service is down (or the node needs to be restarted), the current calculation needs to be halted until the Backfilling reaches up to the start up time. Or else the value will not be as expected.
Brad Mercer commented
I guess because most calculations do not depend on the previous value OSIsoft is not too concerned about this. There would also be a delay in real-time calculations if it were to wait for the backfilling to complete before starting. That said, I'm in favor of being able to select the option for backfilling to be completed prior to starting real-time calculations if it can be done on a per analysis or analysis template basis. I don't know if I'd want a global option to do this for all calculations due to the above.
Kelsey Duffy commented
This would also fix the issue of the backfilled values being "out of order", which has performance implications on the PI archive subsystem as well as preventing them from reaching the update manager (affecting anything naturally scheduled against these tags). Not as important as the example provided since that will be legitimately wrong data, but it's still worth mentioning.
Ivan Berry commented
This is very important. Without this feature the results of analyses that use the previous result cannot be guaranteed.