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02/02/2018
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Hello!
I would like to ask for some feedback regarding the behavior of an OPC UA server.
The client has created a subscription and then added multiple monitored items. The server are sending notifications when values are changing, everything is fine so far. However, after the client has written a new value to one of the subscribed items, then in the next publish response from the server, it returns the status code => BadWaitingForInitialData [0x80320000] on the same node as the client wrote the new value to. The write request is successful and the write response returns “GOOD”. Also, the next publish response from the server (after the error) contains a value and everything is good.
Is the server behaving correctly?
To me this sounds like an implementation issue on the server side, why should the server return this error in a publish response after a successful write request?
// Jonathan
05/30/2017
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https://reference.opcfoundatio…..t4/7.34.2/ Bad_WaitingForInitialData
Waiting for the Server to obtain values from the underlying data source.
After creating a MonitoredItem or after setting the MonitoringMode from DISABLED to REPORTING or SAMPLING, it may take some time for the Server to actually obtain values for these items. In such cases the Server can send a Notification with this status prior to the Notification with the first value or status from the data source.
So it is a server error if the MonitoringMode does not change during your sequence of events.
02/02/2018
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Randy,
Thank you! Your feedback is much appreciated.
I can confirm that the client did not change the MonitoringMode in this case. In fact, the server included a MonitoredItemNotification for the same node with a correct value in a PublishResponse, about 2 seconds before the write request. So this indicates that the monitored item already has been initialized and has obtained the value from the underlying data source.
Thank you once again.
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