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Active PMUs

Nov 28, 2013 at 11:45 AM
I have developed an application to retrieve historical data directly from historian, as described in

The problem I am facing is that the historian is presenting me a set of measurements that contains only null values. I think that somehow during the PDC configuration, a PMU was created and a set of historian IDs were attributed (in my case from PPA:459 to PPA:467). This PMU was then deleted and created again, so a new set of measurements was created (from PPA:471 to PPA:478).

My application retrieves all measurements metadata and constructs a list of PMUs where the PMU names are the "System Name" property and the associated measurements are the "Name" property from the historian. But since I have a deleted / null PMU on my historian, my list has a duplicated PMU.

I have looked into the measurement metadata and I couldn't find any field that could inform if the measurement is active or not.

So here comes my question: How can I check if a PMU is active or not? Can I get it from the historian? Can I get it from the OpenPDC? How?

Dec 3, 2013 at 2:14 PM
Edited Dec 3, 2013 at 2:15 PM
Try issuing the following command to the openPDC console:
INVOKE PPA RefreshMetadata
This will force the metadata in the historian to be rewritten. This generally happens automatically.

A restart of the service will do the same thing.

If this doesn't fix the issue - check the database to see if the other device is still actually there.

Also, with the openPDC service not running you can safely delete the "ppa_dbase.dat" files where your archive files are stored. When the openPDC restarts it will create a new one.

Dec 17, 2013 at 5:42 PM
After doing
INVOKE PPA RefreshMetadata
A restart of the service
The only thing that effectively did the job was
delete the "ppa_dbase.dat" 
Now my historian has 2 types of HistorianIDs: Blank IDs and the real IDs. When I call the webservice, there are hundreds of blank HistorianIDs like this:
Is it possible to erase them from the Historian?

Dec 17, 2013 at 6:45 PM
I think we can add a parameter to the web service to get rid of those.

Are you using 1.5 or 2.0?

If you are using 2.0, I would prefer to just add it that code branch...

Dec 19, 2013 at 6:46 PM
I installed openPDC Configured all my input streams. Everything worked fine. OpenPDC was up and running in less than 10 minutes.
When I accessed the webservice (, the first 120 HistorianIDs are blank:
Isn't this strange?

Dec 19, 2013 at 8:35 PM
This just means these points no longer exist in your local configuration (i.e., database). We can add a parameter, if useful, to hide the blanks from the meta-data service.

These are directly tied to the auto-incrementing ID's in your Measurement table in your database - since no measurements are defined for these points in the database they show as blanks in the meta-data service.