I have a customer with an Ignition system that was very...botched when it was installed. I'm not going to point fingers, but here's the state of the system: the initial project was programmed with PlantPAX AOIs which, if you aren't familiar, are Rockwell Automation's Add-on Instruction, View SE Faceplate package that's supposed to ape some of the functionality of a DCS. These AOIs are very monolithic, "every feature anyone could ever want" type of solution and are thus quite large with hundreds of tags even for something as simple as a digital input.
The programmer recreated the corresponding faceplates in Ignition and left every single tag as Direct, so literally thousands upon thousands of tags all polling at the same time, regardless of whether they're being used on a client or not. Ignition was crashing at least once a week, PLCs were pegged at 100% use at all times....it was a mess.
My customer contact who got hired in after this all happened changed a lot of them over to Leased and put the base rate at zero, which dramatically improved things and the system now runs stable. PLC utliization is still high though.
One other thing the original programmer did was create a separate tag group for every single main UDT tag in the system. Most of them are set to leased with a 0 base polling rate now (the current engineer in charge of the project's doing), but I'm wondering if trimming these tag groups down will improve performance further. I can't for the life of me figure out why someone would go through all that extra work for no good reason, other than it was someone not very familiar with Ignition when they were working on it. I read the manual about tag groups and it doesn't say how they affect performance (could it be Inductive never intended a project to every a group for every tag?).
Anyway, do tag groups have any (however small) negative affects on performance? Will trimming the tag groups down from hundreds to under a dozen improve anything? Is there any reason someone might make a tag group for every UDT instance?