# Ignition & Rockwell PlantPAx v5.0 **URL:** \ **Category:** Ignition\ **Tags:** rockwell\ **Created:** [August 6, 2024, 2:22am UTC](https://forum.inductiveautomation.com/t/ignition-rockwell-plantpax-v5-0/94206 "2024-08-06T02:22:27Z")\ **Posts on this page:** 1\ **Showing post:** 67
**Author:** ![nminchin](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nminchin/32/6911_2.png) [@nminchin](https://forum.inductiveautomation.com/u/nminchin)\ **Post date:** [May 23, 2025, 3:40am UTC](https://forum.inductiveautomation.com/t/ignition-rockwell-plantpax-v5-0/94206/67 "2025-05-23T03:40:09Z")
> [@bwhite](#): > > either an AOI that I create I think it's important to get terminology correct. AOI _ **Parameters** _ can't be grouped into a single read due to the two EnableIn and EnableOut _parameters_ which _cannot_ be set to at least readOnly external access. However, AOI _ **Local tags** _ are perfectly fine to read and _can_ be read efficiently. UDT type _ **members** _ similarly can also be read efficiently. I found no significant difference between reading UDT members, members of aliased UDTs, members of UDTs within arrays, or nested UDTs' members. I noticed a _very slight_ degredation in read speed of AOI Local tags, whether they were UDT types or basic types, but I would consider it negligible. Reading AOI Parameters have _ **significant** _ impacts to PLC response time. On an L82 it was approximately 10x the response time compared to the other tests. Note: all of these results were performed where _every_ tag/member/parameter in the structures read was set to at least readOnly external access. Setting just one to None destroyed performance to approximately AOI Parameter read levels, regardless if the item is read by SCADA or not > [@Ignition & Logix Best Practice Tips for better communications](https://forum.inductiveautomation.com/t/ignition-logix-best-practice-tips-for-better-communications/60386/52): > > I always forget about this... Holy moly Edit: Updated results with tests using different CIP Connection sizes: Test Ext Access CIP Connection Size Tag Count Sample Rate (ms) Actual Sample Rate (ms) Request Count Overload UDTs All Read/Write 500 6787 10 45.48 14 355% UDTs All Read/Write 4000 6787 10 10.06 2 1% AOI Local Tags (UDT) All Read/Write 500 6787 10 50.86 14 409% AOI Local Tags (UDT) All Read/Write 4000 6787 10 10.08 2 1% AOI Parameter Tags All Rea… > [@Ignition & Logix Best Practice Tips for better communications](https://forum.inductiveautomation.com/t/ignition-logix-best-practice-tips-for-better-communications/60386/42): > > I recently decided it was time to actually test the theories with scan rates for different structures in the PLC, and found the results below. What I found (obviously) backed Phil's recommendations to only read UDT tags and to ensure that all members of them are set to at least read access. However what I found was negligible difference in response rate at 100ms when reading the UDT tags from within different structures (e.g. individual UDT instances at the root/controller level, addressing UDT… --- _[View the full topic](https://forum.inductiveautomation.com/t/ignition-rockwell-plantpax-v5-0/94206)._