2 Replies Latest reply on Apr 5, 2018 6:16 AM by WouterR

    Intermittent 'Comm fail' statuses on digital tag


      Hi all,


      At our plant we've set up a PI server, which retrieves data from an interface server. At this interface server, we have several interfaces gathering data from two units.

      Both units have the same interfaces running:

      1. OPC-DA 1 interface for important data (about 30 tags) (for these tags we also have an OPC-HDA interface for history retrieval when the interface fails)

      2. OPC-DA 2 interface for less important data (about 800 tags)

      3. OPC-HDA interface for the rest of the data (about 2-3000 tags)

      4. OPC-HDA interface which only runs when OPC-DA 1 has failed and history retrieval is necessary


      We are in the middle of transferring tags from OPC-HDA (number 3) top OPC-DA (number 2).

      But at the moment we're having an issue on OPC-DA (number 1) of unit 1.

      All tags work correct, except for 1 digital tag, which at random times gives the status 'Comm fail'. Due to that 'Comm fail'. A short time later it is ok again. An example is seen in the table below:



      Number of Values:24
      03-Apr-18 02:10:31LOCAL
      03-Apr-18 02:12:31LOCAL
      03-Apr-18 02:14:31LOCAL
      03-Apr-18 02:16:31LOCAL
      03-Apr-18 02:18:31LOCAL
      03-Apr-18 02:19:37Comm Fail
      03-Apr-18 02:20:31LOCAL
      03-Apr-18 02:22:31LOCAL
      03-Apr-18 02:24:31LOCAL
      03-Apr-18 02:26:31LOCAL


      All other tags on the same interface are working correctly. The same interface on the other unit is working correctly. And this problem started randomly, as far as I can recall, no changes to the PI server or interfaces were done at the time.

      Anyone familiar with this issue?