One of my projects has 5 identical systems (same PLC, same PLC program, same PLC program firmware, and one Ignition Perspective project). The 5 systems share the same Ignition UDTs and tag groups setting. However, one of the PLCs shows significant overload on the sampled rates. Has anyone experienced this before? Is there any explanation for this behavior?
Look at your mean response times. Is the troublesome PLC being polled over a WAN? Or have significant other connections (outside Ignition)? Or has Studio 5000 online all the time?
Also, look at your request counts. Perhaps you have set different buffer sizes and/or concurrency?
(Perhaps you should share the brand, model, and firmware version.)
The troublesome PLC has the same connections as the other PLCs. Other than communication with ignition, it communicates with the same number of remote IO racks and Festos. And no, Studio 5000 is not online all the time.
Yes, I did change the CIP connection size to see if that helps with the overload issue, but not much luck there.
The PLC info:
Phil knows more about this than I do so weight his suggestions higher than mine. That said...
Is anything else connecting to the problem PLC?
I have seen situations where a PLC is overloaded on the layer 3 comms resulting in performance issues with everything connecting to that PLC.
You're pulling slightly more tags and getting a faster response time from the PLC you're not having a problem with. This makes me think you're either having a network issue or you have other things connecting to that PLC and overloading it.
The Class 3 messaging task utilization would be the next thing to check. If the PLC's web page is enabled, that's the easiest way to access it.
Is there another way to check this? It appears the PLC's web page is not enabled.
Rockwell's Task Monitor utility.