OPC UA IIoT Read: BadTooManyOperations

Hello everybody,

Actually, I have something very simple in mind: I have a Siemens S7-1200 PLC with an OPC UA server, from this I want to read a set x of variables with their values.

The whole thing is structured as follows: The Browese Note gets regularly an Injection and the Read Node reads out the variables from the corresponding namespace:

With a small number of 33 variables this works without problems. But if I increase the number to 53 variables I get the following error message from the read node:

I found two explanations on the Internet about "BadTooManyOperations":

  • Reach the limit of what the server is capable of handling in term of monitored item
  • The request could not be processed because it specified too many operations

In the PLC you can set the maximum number of monitored elements, this is set to 200 by default, I have increased it to 500. Nevertheless, I got the error message again.

If I select in the Read Node at "Attirbut Id" e.g. Node-ID or value, it works without error message.

But this is not what I want, because I need all attributes for a further evaluation.

Does anyone have an idea how I can fix the error message?

Thanks for your help

No. But you could switch to using s7 protocol instead of that is an option for you and avoid OPC altogether?

Thank you Steve-Mcl for your answer.

I want to use the flow for Siemens and for B&R and maybe other PLCs, so I have to fix this error message.

Hi. Just because you use multiple PLC types doesn't mean you have to use OPC UA for all PLC's. I work with a variety of PLC's and use the best node for the job. Data collection is the easy part or the whole job - but it needs to be the most reliable.

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