Backfill To vs Remove Old Data
How are Backfill To and Remove Old Data related? Below are the definitions from the documentation.
So Backfill To will be leveraged anytime the calc is saved or the calc service is started up? If I put 1/1/24, and in 5 years I reboot the machine, will Calcs calculate 5+ years of data? Will it add the data to the historian? Ignore it since it's already there?
Remove Old Data, will that only come into play if I check the box and save it? What if the Backfill To is older than the Remove Old Data? Say Backfill To is 1/1/24 and Remove Old Data is 6/1/24. Will it remove data back until 6/1/24 and then backfill to 1/1/24?
Backfill To - date/time the calc/event will backfill to upon initially starting. A Data Range will appear next to the date/time picker once an expression is created and the Evaluate button is clicked. This data range indicates the history of data available for the input tags used in the calculation.
Remove Old Data - if checked, old calculated data will be removed from the Historian and the backfill process will restart using the 'Remove From' date/time as its starting point. Any data before the Remove From date/time will be left intact.
3 replies
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Hi
Backfill To is used on the initial backfill when the calc is created. It will backfill from that datetime up until now. If it is an asset-based calculation, new assets will backfill from that datetime as well when they come online. Every time a calc is triggered it updates and saves this latest datetime in the database. That way, if the calc is turned off or the calc service is stopped for some period of time, it knows when it last calculated and can backfill to catch back up to live mode. So if you create a calc that runs for some time then you turn it off for 5 years, it will backfill 5 years worth of data when it comes back on.
Remove Old Data is used to go back and recalculate data from the configured datetime. Typically, this would be used if comms were down and you had periodic calculations which you knew were erroneous because of latent data. Prior to 24, you had to start over from the beginning which could take a while depending on the number of assets and the history of data. But now, you can go to the specific time and recalculate up until current time. With the Remove Old Data time picker, you can actually choose any point in time to back to and recalculate, even before the original Backfill To date.Hope this makes sense!
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