Using a ShouldPreReadData Registry Key

About this task

Use a ShouldPreReadData registry key when your calculation tags use AddData to write to tags that are also used as trigger tags or used in calculation formulas such as CurrentValue("MyTag")+5.

If you want to skip the pre-read of data and have Calculation Collector query data at tag processing time instead, you have to make a registry key on the machine running the Calculation Collector.

Use the following steps to create a value as a DWORD for ShouldPreReadData registry key.

Note: This registry key cannot be performed on a Server to Server collector scenario.

Procedure

  1. From the Start menu, select Run and enter Regedit.
  2. Open the following key folder HKEY_LOCAL_MACHINE\Software\Intellution, Inc.\iHistorian\Services\CalculationCollector\.
  3. Create a value as DWORD called ShouldPreReadData and set it to zero value (to have the calculation collector skip pre-reading of data, set this value to 0).
  4. Click OK, and close the Registry Editor.
  5. Restart Calculation Collector for the changes to take effect.