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OPC Items coming asynchronously several seconds after OPC server connection -> unwanted side effect.

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22 Nov 2014 17:45 #2525 by support
You should be able to increase the delay after the server is disconnected, by setting the delay value (in milliseconds) to the following property:
easyDAClient.InstanceParameters.HoldPeriods.ServerDetach

It should be noted, however, that an OPC server that changes its address space is essentially not conformant with the OPC specification (quote taken from OPC DA 3.00 Specification):

2.6 The Address Space and Configuration of the Server
[...]
It is expected that this server address space is stable and is managed within the server.
[...]

Best regards

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21 Nov 2014 07:42 #2524 by Emilio
Hello,
this topic is not exactly the same like a previous one posted by me. It is slightly different, that is why I decided to post a different one. The use case is different.

The use case:
In our application, the user browse first any OPC server.
Then he goes to a mapping page where he can map OPC items for some other purpose, not relevant here.
After browsing the server the whole OPC tree is saved for the mapping functionality.
The OPC server is NOT used anymore directly.

I calculated manually about 4/5 seconds timeout, after that the OPC server will be automatically disconnected.

The problem:
OPC items that come into the tree some second after the connection, asynchronously, are NOT available after the first browse.
When the user recognizes that some item is still missing, he browses again but it is too late, the OPC server will be connected again and the same items shall be found, the "fastest" coming into the tree.

The "slowest" shall never be available!

To clarify exaclty what I'm asking:
I can implement several workarounds to solve this issue, it is not difficult, for example keep internally browsing some node with 1 second frequency just to keep the server alive.
I'd rather prefer a good tehoretical way, whenever it is already available in the OpcLabs library.

Is there any possibility to increase the connect timeout, which might be too short for our purposes?
I haven't found it in the Concept Document.

Thanks for support.
Emilio

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