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OPC HDA Server tag unknown to DVCH

I'm getting a very strange error message.  It says that a given tag on the DeltaV OPC HDA server is unknown to the DVCH.  The tag exists but is not in the historian and never has been that I know of.  The HDA server connects to a OPC HDA interface to send data to PI.  The tags in question are not in PI either.  I looked at the HDA server with the HDA Tool that comes with the PI interface and I don't see any of the tags in question on the HDA server.  Any suggestions on how to troubleshoot this?  I'm puzzled.

Kent

• 19 Jun 2026 3:53 PM
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2 Replies

• Andre Dicaire

  

  • 19 Jun 2026 6:15 PM

  My first thought is the history tag is different than what you think.  The history tag can include or omit the .CV field.  Or the parameter has been abstracted in the module to a module level internal reference, and FIC-101/AI1/PV is historized as FIC-101/PV  (with or without CV).

  Check the Module's History Collection to confirm the tag is configured exactly as you are trying to read it.  

  If configured, check it hasn't been disabled.

  

  You can also check the PHIST.SCR file located in the DVDATA/Download folder of the historian.  This the downloaded runtime configuration of the historian, so if it's there, then you know the configuration database is in line.  

  Hopefully, you find a discrepancy that explains what you are seeing.  If the PHIST file has the tag as you are searching for it, we have a mystery and a call to the GSC is likely warranted.

  When using PHV to view history, DeltaV does not have a focused list of configured available history tag.  You browse the entire name space, in case you want to trend a value in real time that is not historized.  But if you don't know the historized tag path (syntax), you have to try variations or check the History collection of the tag.  Wouldn't it be nice if you could enter or browse a tag and see select from the focused list of historized tags of that module?  Hmm.  Then you wouldn't have to guess the tag name or navigate the module parameter tree to get to the tag you think you want.  

  good luck.

  Andre Dicaire

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• Kent

  

  • 19 Jun 2026 6:32 PM

  In reply to Andre Dicaire:

  Thanks for the quick response. The problem is that the error often, but not always, is for a tag from an AI block that feeds a PID block. The only time I historize a value from the AI block is if I'm filtering the PID PV and I also want to be able to see unfiltered as well as filtered data. There are also quite a few that are calling for OUT and SP from a DC! block when I only historize PV. Very puzzling.

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