4 Replies Latest reply on Feb 27, 2018 9:25 PM by KarlRickards

    OPC DA ReadOnly Migration


      I'm in the planning phase of migrating a PI OPC DA Interface to a newer ReadOnly version.  The only information in the user guide is a link to Live Library that has a 9 step approach.  However on the final step where it instructs you to start the interface, there seems to be a gap of information in regards to what to do with the existing interface apart form uninstalling it once you're finished.  My main concern is there will be 2 interfaces with the same pointsource and interface ID running simultaneously.  Will PI handle running 2 interfaces with the same pointsource and ID for a short period of time without doubling up values while I transition from one interface to the other?

        • Re: OPC DA ReadOnly Migration

          You don't want to have two interfaces (Read/Write and also the ReadOnly) running at the same time for very long. From KB00093 "Other than for interface failover, OSISoft discourage allowing multiple data sources to write to the same point".


          Technically though you can do it for a short while. I assume both are on the same machine.


          The pibufss sorts out the compression before sending to PI so you shouldn't get the doubling up of data. You shouldn't get the [-11414] errors since both instances will be using pibufss.


          If both instances send the same data at the same timestamps you may see the "[-109] Value at This Time Already Exists" error messages on tyhe interface node logs.


          If you use the same pointsource and location1 and basically are copying over the Read/Write bat file contents to the ReadOnly bat file, check that you don't have any output points still left over from the ReadOnly instance.

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          • Re: OPC DA ReadOnly Migration
            Steve Boyko

            Usually you stop the old one and immediately start the new one, accepting that there will be a small gap in data when neither interface is sending data to PI.

            • Re: OPC DA ReadOnly Migration

              Hello Karl,


              As Stephen and Steve have pointed out, basically: never use two interface instances with same pointsource and ID simultaneously!


              If You do the migration on the old IF node, it's easy. Just follow step 1-8, stop the old, then start the new instance.


              If You also replace the old machine with a new node, I suggest to make sure if it's fine before the go-alive.
              To do that I usually create an 'OPC_test_temporary_tag', similar to the others, but with a temporary pointsource, fetching data from the same

              OPC server. Have to make sure that the new node is connects correctly, buffering well and fully functionable. If yes, just set the final

              pointsource, stop the old IF and start the new one.


              In both case, if having problem with the new, You can still restart the old IF. (But always running just one of them, to avoid further troubles! : )

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              • Re: OPC DA ReadOnly Migration

                Thanks everyone.  Stephen Royce's answer pretty much confirmed my suspicions but also highlights that the documentation on Live Library is missing a couple of crucial elements.  Anyone who manages a data historian will in any case try to avoid losing data and guiding administrators how to successfully migrate with that aim in mind should be first and foremost.