Applies To:
  • CitectSCADA 5.4x, 5.5x, 6.xx, 7.xx
  • CitectHMI 5.4x, 5.5x, 6.xx, 7.xx
Summary:
I am using CitectSCADA version 6.10 spk A and have been trying to get trend backfilling to work.  I have set both [Trend]Redundancy=1 and [Trend]EnableBackfill=1 and I have tried setting values to the [Trend[GapFillSamples parameter, for example 1000.   I have found that unless I set the [Trend]GapFillSamples parameter to -1, backfilling does not seem to occur on startup.  

Solution:
Setting [Trend]GapFillSamples to -1 uses the Time mode.  In situations where there are trends of varied sample rates, it is preferable to instead use the [Trend]GapFillTime parameter.  For example, for a 10 second sample trend, It makes sense to try and fill gaps that are so many seconds large (default 10000 ms) whereas is is not usual to expect 1000 samples (in example above) to be missed before a gap is recognised.  There will always be a disparity between the filling of fast and slow sample trends if you use [Trend]GapFillSamples.  I recommend always using the time method.  
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