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OPC UA Arrays

Michael Meirovitz

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02/24/2014

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08/02/2021 - 12:13

Hi,

I have few questions regarding arrays in OPC UA.

What is the maximum number of elements in an array?
How can the OPC client determine what is the number elements in an array?
Does the OPC Server sets the number of array items? Or, is it set by the OPC client?

Thank you.

Mike

Randy Armstrong

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08/02/2021 - 13:33

1) The max number of array elements depends on the server and the variable.

The ServerCapabilitiesType defines the Server wide limits:
https://reference.opcfoundatio…..rt5/6.3.2/

Per Variable limits use the properties defined here:
https://reference.opcfoundatio…..rt3/5.6.2/

2) The number of elements in an array are encoded with the value in the Variant structure.
https://reference.opcfoundatio…../#5.2.2.16

If a Variable has a fixed length array you can used the ArrayDimensions Attrribute:
https://reference.opcfoundatio…..rt3/5.6.2/

3) If a Variable does not use fixed length array then the Client can write arrays that have any length.

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