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Intermittent 'Comm fail' statuses on digital tag

Question asked by WouterR on Apr 3, 2018
Latest reply on Apr 5, 2018 by WouterR

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?