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Monitored Tag changed DataValue value type during subscription
April 19, 2023
18:36, EEST
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Jeremy Morgan
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This is a bit of a strange one. We are monitoring Integer OPC Tag by the usual method (Subscription etc.).

We had a incident recently where for no apparent reason the MoniteredDataItem new DataValue contained a Boolean type rather than the expected Integer.

“value=DataValue(value=true, statusCode=GOOD (0x00000000) “The operation succeeded.”, sourceTimestamp=null, sourcePicoseconds=0, serverTimestamp=04/18/23 00:35:02.7936037 GMT, serverPicoseconds=0)”

This happened repeatedly for serveral hours until we restarted our application.

Then then correct type of data was shown:

“value=DataValue(value=108, statusCode=GOOD (0x00000000) “The operation succeeded.”, sourceTimestamp=null, sourcePicoseconds=0, serverTimestamp=04/18/23 05:05:25.4785319 GMT, serverPicoseconds=0)”

Unfortunately, I don’t have the logs around the time when the systen transitioned into the unusual behaviour.

During the erroneous period viewing the Tags with Prosys Client showed the correct Integer values.

Is there any mechanism you can envisage that would cause a MonitoredDataItem’s DataValue to be returned as Boolean rather than Integer?

April 20, 2023
8:17, EEST
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Matti Siponen
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Hello,

That is very odd. We would need some additional information on this:

Have both the Client and the Server been developed with Prosys OPC UA SDK for Java? If either of them has been developed with the SDK, could you check which version or versions of the SDK they have developed with?

When you say “Integer OPC Tag”, could you confirm that this means an OPC UA Variable Node with Integer as its DataType? Confirming this is important because if the DataType is BaseDataType instead, then it would be allowed for the Node to have both Integer and Boolean Values. Could you also confirm that you’re talking about OPC UA and not OPC Classic?

When you say “This happened repeatedly for serveral hours until we restarted our application”, could you specify which application or applications you restarted?

When you say “viewing the Tags with Prosys Client”, could you specify what do you mean with Prosys Client? Do you mean one of our Client applications, such as Prosys OPC UA Browser, Prosys OPC UA Client for Android, or a Client developed with the SDK?

April 21, 2023
19:59, EEST
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Jeremy Morgan
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Apologies for not being clearer.

“Have both the Client and the Server been developed with Prosys OPC UA SDK for Java? If either of them has been developed with the SDK, could you check which version or versions of the SDK they have developed with?”
The Server is Kepware OPC V6.10. Our OPC UA client is using Prosys OPC UA SDK for Java 4.10.2-62.

“When you say “Integer OPC Tag”, could you confirm that this means an OPC UA Variable Node with Integer as its DataType?”
I believe so, but I will get this checked and follow up in the thread.

“When you say “This happened repeatedly for serveral hours until we restarted our application”, could you specify which application or applications you restarted?”
This was our Java OPC UA Client application which runs as a Wildfly service on a Linux server.

“When you say “viewing the Tags with Prosys Client”, could you specify what do you mean with Prosys Client? Do you mean one of our Client applications, such as Prosys OPC UA Browser, Prosys OPC UA Client for Android, or a Client developed with the SDK?”
It was with Prosys OPC UA Browser on a Windows PC.

April 24, 2023
9:36, EEST
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Matti Siponen
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Hello,

We would recommend you to contact the manufacturer of the Server regarding this behavior. The DataValues MonitoredDataItems receive from Servers are not modified on the Client side so this would seem to be a Server side error.

Restarting the Client would cause the Server to delete and recreate Subscriptions and their MonitoredItems. Even if this would fix the issue, it would still be an error in the Server that it somehow got to a state where it reported Boolean Values for Integer Variable. Though, it is still possible that the Variable being monitored has DataType of BaseDataType and thus it would support having both types of Values.

April 24, 2023
15:27, EEST
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Jeremy Morgan
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Thanks for the reply.

It doesn’t look like I can post a screen shot here, but both the items are showing in the Prosys Browser as DataType UInt32. That corresponds with the native type in the OPC server (DWORD).

I presume it would show DataType as ‘BaseDataType’ in the Prosys Browser if that were the case (i.e. if it would support both values)?

April 24, 2023
15:51, EEST
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Matti Siponen
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Hello,

The DataType displayed in Browser is the value received when the DataType Attribute of the Variable Node was read. If this value is UInt32, then it would suggest that all Values of this Node should be of that DataType. If the Variable Node supported both Boolean and UInt32 Values, its DataType should be BaseDataType.

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