I have PI AF analysis which runs every 12 Hours and store the value in PI DA. when ever it runs it store actual value once and zero value once at the same time stamp.
Can you share a little more about the analysis expression? Also, what is your output time stamp configured for? Are you using trigger time, execution time, or relative to trigger time? If you perform a recalculation, (making sure the values are deleted first), do you also get two values written at the same time-stamp? Is it possible another analysis is writing to the same tag? Did you try stopping to the analysis to see if something else is writing to the tag?
As Dan Fishman mentioned above, most of the time we see duplicate different data in an analysis output, it is due to multiple analyses writing to the same output. If you don't know which analysis it is, feel free to contact Tech Support as we have an internal tool we can use to tack down the analyses.
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