Emerson Exchange 365

Continuous Historian Data Extraction

Hello,

I'm trying to extract data from the Continuous Historian for the sake of performing miscellaneous mass-data analysis, including but not limited to Alarm Rationalization. We have V14.3.1.

I have successfully extracted data for one point at a time using the DVCHDUMP utility. Documentation for the utility seems a bit scattered, but if you play with it a bit you can sort of find your way around. I can make this tool do what I need it to do by creating a script that will run this utility over and over for all of the tags I desire, saving the results in text files in a folder.

However, I have some reservations:

• Will requesting an enormous amount of data for 1000+ points (one at a time via DVCHDUMP) stress the system?
• Is there not a better way?

I tried pulling one of the .DB files from D:\DeltaVHistory and opening it locally but it appears to be encrypted or unrecognized by the DB Browser I tried.

Does anyone have any sage advice that may help me get data in a better way?

Thanks,

Josh

• DeltaV #Analytics #DCS

Joshua Granger

• 9 Aug 2021 3:51 PM
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4 Replies

• LaurentB

  

  • 9 Aug 2021 4:09 PM

  Hi
  DVCHDUMP is the much better way to extract large amount of data from DVCH Historian (DV reporter is not enough to do it)
  I think there is no other way to do it.
  Creating BAT file is working but it can stress the historian station ( not entire system). The large number of tags is not the criteria , its's depends of the period required and of the scan time. At the end the ressource depends of the number of sample to extract.
  CPU ressources has to be considered but also the disk space for extracted data , several giga could be necessary !!
  I already did such type of extraction for very large samples and to avoid DV application stress I did it on a separate simulate plateforme by only transfering compressed XFC data from real DV system to a simulate. The scripts ran for several days to extract 200 Go of data .

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• Joshua Granger

  

  • 9 Aug 2021 6:08 PM

  In reply to LaurentB:

  Great! Thanks for the response.
  
  You reminded me - it appears that the "raw" request will give data when it either changes by a large enough amount (1% or so) or 10 minutes has passed - whichever comes first.
  
  Do you perhaps know how to request data to be interpolated for a given desired period? For example, I want to extract data interpolated for 30-minute intervals (00:00:00, 00:30:00, 1:00:00), etc. I was thinking maybe that's what "RESAMPLED VALUES" meant but so far I have not had luck.

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• LaurentB

  

  • 9 Aug 2021 6:15 PM

  In reply to Joshua Granger:

  Huumm yes we can, but i have to remind back the syntax. It’s not possible to keep it in my head as it’s a complex syntax ;-) if somebody have the answer that’s avoid me to find it back !!!
  Typing dvcchdump without any argument will show you a basic help…
  Let me few days more :-)

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• Duane Harnish

  

  • 9 Aug 2021 7:30 PM

  In reply to LaurentB:

  Common examples:
  
  Desire raw data for a specific parameter (e.g. PID_LOOP/PID1/PV.CV) for the last 5 minutes
  dvchdump raw PID_LOOP/PID1/PV.CV now now-5m
  
  Desire raw data for a specific parameter (e.g. PID_LOOP/PID1/PV.CV) for the last 5 minutes from a different DvCH Continuous Historian (rather than the local one)
  dvchdump raw /NODE=RemoteDVCHNodeNameHere PID_LOOP/PID1/PV.CV now now-5m
  
  Raw data results will be saved in D:\note1.txt
  dvchdump raw PID_LOOP/PID1/PV.CV now now-5m >> d:\note1.txt
  
  Desire raw data for a specific parameter (e.g. PID_LOOP/PID1/PV.CV) for a specific time period (in GMT)
  dvchdump raw PID_LOOP/PID1/PV.CV "2006/08/01 12:00:00.000" "2006/08/02 12:00:00.000"
  
  Desire list of all tags that are currently being historically collected, or are no longer being collected and still within the Continuous Historian's database:
  dvchdump tags
  
  Desire list of all "holes" in the data for a specific parameter (e.g. UNSOLOSTRESS015/PARAM1.CV) for the last 24 hours
  dvchdump holes UNSOLOSTRESS015/PARAM1.CV now-24h now
  
  Desire list of a subset of tags (those with "PID" anywhere in the parameter path) that are currently being historically collected, or are no longer being collected and still within the Continuous Historian's database:
  dvchdump tags *PID*
  
  Desire the Minimum, Maximum, and Average values for a specific parameter for the last 24 hours
  dvchdump PROC CONTROLLER_NAME/FRETIM.CV AVE,MIN,MAX now-24h now
  
  Tips:
  The parameter path is case sensitive (so use ALL CAPS for the parameter path)
  DvCH data is stored using GMT timestamps, so make all explicit time-based requests with that in mind
  Timestamps for raw data within DvCH are as of when the data was received by the DvCH Server (not as of when the data was provided by the source node)
  Unless the /NODE option is used, the data will be retrieved from the local DvCH Server

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