Maximum history values displayed

Questions regarding the use of the UaExpert.

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induna23
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Maximum history values displayed

Post by induna23 »

Hi,

I tried to retrieve the history values of 5 nodes in my address space each having atleast 2000 values.

But UAExpert gets disconnected and again reconnects in this scenario. It doesn't display the values and shows watchdog timeout. If I try to do a cyclic update immediate I am able to see the updated values.

Is this a problem with the client that its not able to show enormous amount of data in the viewer because of which it gets disconnected ?

Thanks & Regards,
Indu

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Re:Maximum history values displayed

Post by Support Team »

Hello,

as you are getting a watchdog timeout error, it seems likely that your server is not responding to the watchdog reads of UaExpert while reading the history values. Please ensure that the watchdog reads are getting handled correctly and in a reasonable time.

Also ensure that all timeout values in the UaExpert settings are set to appropriate values if your server takes long time for processing the history read requests.

Additionally, you can limit the amount of history values returned by the server by changing the 'HistoryPlugin.NumValuesPerNode' parameter in UaExpert (provided that your server handles this parameter correctly).

Best regards
Unified Automation Support Team
Best regards
Unified Automation Support Team

induna23
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Re:Maximum history values displayed

Post by induna23 »

Hi,

Thanks for the help. I am able to view the values in the graph without connection timeout.

I have another query :

History values for NodeA between 11.00hrs - 20.00hrs
is shown as 5000.
But the history values for the same node between 10:00hrs - 20.00hrs is lesser than 5000.

Does the MaxHistoryNextCall play some role in displaying lesser values ?

What is the purpose of MaxHistoryNextCalls parameter in the UAExpert settings. Its default Value is 1000 in the settings.
How does it affect the History values returned by the server ?

Thanks & Regards,
Indu

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Re:Maximum history values displayed

Post by Support Team »

Hello,

the 'HistoryPlugin.MaxHistoryNextCalls' parameter is intended to protect UaExpert from erroneous servers or very large amounts of results. When doing a HistoryRead, a ContinuationPoint might be returned by the server for getting the next data set. An erroneous server might return a ContinuationPoint for every HistoryRead call, leading to the UaExpert calling HistoryReadNext infinitely.

Hence, this parameter sets a maximum of HistoryReadNext calls the UaExpert does before stopping to retreive more values. The value should be high enough for normal HistoryRead, but it might be necessary to increase the value for servers returning large amounts of data.

If the server returns less data for a bigger timespan, please recheck the server's responses for correctness - UaExpert just displays all values delivered by the server.

You might want to have a look at the responses using the CTT Tool of the OPC Foundation in 'Analyzer Mode'.

Best regards
Unified Automation Support Team
Best regards
Unified Automation Support Team

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Re:Maximum history values displayed

Post by Support Team »

This topic is solved and has been locked by the administrator.
Best regards
Unified Automation Support Team

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