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Thread: OPCUA: Changing the parameter QueueSize for a monitored item

  1. #1
    Join Date
    25.01.2019
    Posts
    2

    Default OPCUA: Changing the parameter QueueSize for a monitored item

    Is there any way to change the queueSize for the monitored items.
    I have checked via wireshark: RequestedParameter QueuSize is everytime 1.

  2. #2

    Default Re: OPCUA: Changing the parameter QueueSize for a monitored item

    Hello Savenni,

    Thanks for your post and welcome to the forum!

    The AccessOPCUA OPC UA server in the process gateway accepts different queuesizes suggested by the OPC UA client.

    The OPCUA32 OPC UA client driver for zenon, currently uses a fixed queuesize of 1.

    Do you have a specific use case for a larger queuesize? (e.g. durable subscriptions, high volume data changes between subscription execution, ...)

    Best regards,
    Mark

  3. #3
    Join Date
    25.01.2019
    Posts
    2

    Default AW: OPCUA: Changing the parameter QueueSize for a monitored item

    Hi Mark,

    thanks for quick reply.

    The task is to transport time stamped events from a SPS to HMIs alarm system via OPCUA.

    OPCUA has the AC specification for this. Our OPCUA server supports that feature but I found no support at any HMI system today.

    There exist (lets say) a trick to got it work: When OPCUA server is prepared for that you can set the sampling interval to zero and adapt the queueSize to a value > 1.
    Setting the sampling interval to 0 is supported by ZENON but queueSize is every time 1.
    The queue size should be adapted to a value that no event value change is gone lost (depending on frequency of this values changes and publish interval of the OPCUA subscription).

    But possibly there a is better way in ZENON to transport events to its database.
    Please be aware that these events can created in sub milisecond region (> 200 Ás).
    This is used to have the correct order of events. Without that you can't find the root cause e.g. in case of a fault.

    My feeling is that other systems should have the same problem with OPCUA. Isn't it?

    Regards.



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