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  9. Problem in Reading Multiple Item Values.

Problem in Reading Multiple Item Values.

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29 Oct 2014 14:24 #2471 by support
Replied by support on topic Problem in Reading Multiple Item Values.
Thank you for more info.

I have checked the code that relates to this error check (for the first problem), in the version you have and in the current versions. I could not see any apparent significant difference. It is therefore unlikely that upgrading to newer version will resolve your problem #1, though it is still recommended. Using OPC Analyzer would be highly beneficial.

Please also implement the workaround suggested, with synchronous reads.

The TypeInitializationException you refer to only occurred to that customer under specific circumstances, namely 1) his system was quite slow and busy during startup, and at the same time 2) he was starting multiple apps written with QuickOPC at once. We have just allowed a longer timeout to cope with a busy system. This should now be resolved.

Best regards

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  • saravana48
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29 Oct 2014 12:54 - 29 Oct 2014 13:13 #2470 by saravana48
Replied by saravana48 on topic Problem in Reading Multiple Item Values.
Thanks for Response.

1) QuickOPC version - 5.12.1308.1
2) Top Server version - V4.200.353
3) The Top server is in remote machine.
4) The error occurs randomly.

Have you completely fix the System.TypeInitializationException in the post (www.opclabs.com/forum/general-issues/1388-system-typeinitial...asydaclient-threw-an-exception), because configuring the mutual exclusion's timeout value from config file have the possibility to throw the error.

Only after the fix, I will upgrade to the latest version 5.23.1225.1.
Last edit: 29 Oct 2014 13:13 by saravana48.

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28 Oct 2014 15:29 #2467 by support
Replied by support on topic Problem in Reading Multiple Item Values.
Which version of QuickOPC are you using please?
Which version of the Top Server are you using please?
Is the server on the same computer as the client, or is it remote?
Do these errors happen always (or under certain conditions), or randomly?

ad 1) The reason for the error is explained in the message text. It means that we have issued an asynchronous read call, where the item to be read are identified with their handles. The responded with a callback containing the results, but it did not send us the results for all the items originally requested - which is against the OPC specs. Normally I would tell you to go to resolve this with the server vendor. However, Top Server (from Software Toolbox) is one of the most common servers on the market, and usually very reliable. For this reason, I'd rather suggest that you put a special tool (OPC Analyzer) between the client and the server, and we would analyze the OPC communication and determine where the fault is.

Since this error is only possible with asynchronous OPC calls, you should be able to work around it by switching to sync-only calls, like this:
EasyDAClient opcComponent = new EasyDAClient();
opcComponent.Isolated = true;
opcComponent.InstanceParameters.Mode.AllowAsynchronousMethod = false;

ad 2. I cannot determine the reason - probably the OPC Analyzer would be the way to go as well.

Best regards
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28 Oct 2014 14:03 - 28 Oct 2014 14:15 #2466 by saravana48
Problem in Reading Multiple Item Values. was created by saravana48
The following the errors are raised while reading multiple items values from OPC server(Top server) using Quick OPC Classic.

Code:

Dim objOPCItems As DAItemDescriptor()
Dim objResult As ValueResult()
Dim objOPCServer As ServerDescriptor
Dim m_opcDAClient As New EasyDAClient

m_opcDAClient.HoldPeriods.TopicRead = 1000
m_opcDAClient.Timeouts.ReadItem = 5000

objOPCServer = New ServerDescriptor("AAA", "BBB")
objOPCItems = New DAItemDescriptor(asTagNames.Length - 1) {}

For iTagCount = 0 To m_objOPCTagManager.m_asOpcTagNames.Length - 1
objOPCItems(iTagCount) = New DAItemDescriptor(asTagNames(iTagCount))
Next

objResult = m_opcDAClient.ReadMultipleItemValues(objOPCServer, objOPCItems)

Error Details:
1) Message : Item not in callback. The OPC callback does not contain an entry for an expected item. Most likely this error indicates an implementation bug in the OPC server.
Code : -1073442802

2) Message : Cannot connect Data Access client (timeout). (-1073430527)
Code : -1073430527

I have set the timeout value as 5000 milliseconds(Timeouts.ReadItem = 5000), but it took more than 65 seconds to throw the timeout error.

What is the reason for these errors?
What are the changes to be made to overcome these errors?


Thanks in advance.
Last edit: 28 Oct 2014 14:15 by saravana48.

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