Applies To:
  • CitectSCADA 5.xx, 6.xx, 7.xx

Trend gap filling occurs in two scenarios, backfilling of missed samples from another trend server and filling trend gaps with interpolated values.

Redundant Trend Backfilling
For a redundant trend system, if one trend server has missed trend samples since its last restart, it can obtain these from the other trend server if they exist for the missing periods.
All it requires is that the other trend server obtained samples from the io server (local or remote) and the specific io device and recorded them or has cached them for recording to file.

This can be used to disable redundant trend server backfilling on startup and server reconnection.

Interpolated Gap Filling
The other gap filling that can be employed is where trend samples have been missed due to performance issues affecting the obtaining of the trend samples for any required sample time. Please note, this is not the same thing as trying to fill a trend gap where the io device has been offline.  Trend samples that were missed because their io device is offline are bad data and are NOT gap filled.

The Trend Gap Fill Parameters:

This determines the method (Step or Ratio) to use for interpolating (non io device communication failure) missed samples

This determines if gaps are filled base don the number of missing samples and how many missed samples constitutes a maximum gap to fill. 
If set to -1 this is ignored and GapFillTime is used instead.  Otherwise GapFillSamples is used.

[Trend]GapFillTime - determines if gaps are filled based on their time and what is the maximum size (in time) gap to fill. 
If set to 0, this is ignored and GapFillSamples is used instead.

Check the Help for the version you using for further information and allowable parameter values.