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OPC UA freezing problem

Timo

Hi,

Our plant has a Siemens S7-1500 with an OPC UA server. Citect Scada 8.1 (update 28) communicates with logic with the OPC UA client. If, for some reason, Citect cannot read the variables from the logic, the variables will be displayed in #BAD. After a while, all the variables whose value is constantly changing start to show the current value again. Variables with a static value (such as pump status) remain #BAD and do not recover until the Citect IO server is restarted. OPC UA client version is 4.01.04.000.

Is there any parameter to force the OPC UA client to read all variables?

I can't find in-depth information on Citect's OPC UA client, so any help is needed.

  • Hi  ,

    Driver debugging is best handled by AVEVA Customer Support. I'd recommend reaching out to them.

    There are debugging parameters to help understand what issues are occurring. See the opcua.chm file for details.

    [OPCUA]

    DebugLevel

    DebugCategory

    DebugUnits

    It could be a physical connection problem or the OPCUA Server rejecting messages? It is hard to know.

  • Hi Timo,

    The OPCUA driver uses OPC UA Publish/Subscribe mechanism to get value updates. It does not use Read/Polling services to read all tag values. There is no parameter to enable reading all tags.

    The values will be displayed as #BAD if the driver loses the connection to the server. When the connection is re-established, the driver will recreate OPC UA items for all Citect tags (item monitoring mode set to “Disabled”) and will change the monitoring mode to “Monitoring” for tags which are subscribed in Citect.
    After that the server should send value updates for all subscribed tags. If it does not do it, it is likely a server issue.

    If there is some problem on the driver side, you will need to engage support. They would need the driver and wireshark logs at a minimum.

  • in reply to Olivier

    Hi,

    Support noticed this incident (or did you provide a hint?) and they made this as a support case.

    The problem was solved with two additions to the OPC UA I/O-device configuration:

    Background Poll --> TRUE

    Min Update Rate --> 00:00:05

    Finally, I updated the Citect TCP driver, and the last little problem was fixed.

    Thanks.

  • in reply to Timo

    Good to know your problem has been resolved. Just curious, are you using the encrypted communication in this OPC UA protocol?

  • in reply to Jacky Lang

    No encryption. We try to keep things simple if it’s safe.

  • in reply to Timo

    Thanks Timo. So, we can eliminate the encryption that caused the original problem. Enabling the backrgound poll means that once an OPC UA  variable tag is subscribed, it will be changed to the "Reporting" mode and always in that mode until the session ends. Without the background poll, those tags on a page will be changed to the "Disabled" mode when you are navigating away from this page. I suspect that the server may not handle well the frequent changes of monitoring modes, especially for those tags with "static" values.

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