# Allen Bradley SLC communication overload **URL:** \ **Category:** Ignition\ **Tags:** ignition83\ **Created:** [September 16, 2026, 9:09am UTC](https://forum.inductiveautomation.com/t/allen-bradley-slc-communication-overload/117096 "2026-09-16T09:09:51Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![pgmo](https://avatars.discourse-cdn.com/v4/letter/p/d07c76/32.png) [@pgmo](https://forum.inductiveautomation.com/u/pgmo)\ **Post date:** [September 16, 2026, 9:09am UTC](https://forum.inductiveautomation.com/t/allen-bradley-slc-communication-overload/117096/1 "2026-09-16T09:09:51Z")
What does the following picture mean for an Allen Bradley SLC device ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/5/9/597bc20405bbb9ef363fcb9dba4127e10255029d.png) Shall I worry? How can I improve? Ignition **8.3.8 (b2026071409)** Thanks in advance, regards ---
**Author:** ![Jasmine\_Quick](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/jasmine_quick/32/80380_2.png) [@Jasmine\_Quick](https://forum.inductiveautomation.com/u/Jasmine_Quick)\ **Post date:** [September 16, 2026, 9:12am UTC](https://forum.inductiveautomation.com/t/allen-bradley-slc-communication-overload/117096/2 "2026-09-16T09:12:07Z")
It means the plc cant keep up with the comms load to Ignition/the rest of the network. You should be seeing laggy tags, missing trend data etc for any connected to this plc as a result. What SLC are you connected to? Can you upgrade? ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [September 16, 2026, 12:21pm UTC](https://forum.inductiveautomation.com/t/allen-bradley-slc-communication-overload/117096/3 "2026-09-16T12:21:53Z")
> [@pgmo](#): > > Shall I worry? Yes. Any overload above a few percent indicates a real problem--your tags aren't being scanned at the configured pace. > [@pgmo](#): > > How can I improve? Check your PLC's status file for these settings, first: > [@Typical Performance between Ignition and AB SLC 5/05](https://forum.inductiveautomation.com/t/typical-performance-between-ignition-and-ab-slc-5-05/17262/3): > > Check “Comms Servicing Selection” and “MSG Servicing Selection” for channel 1 (S:2/15 & S:33/7). If either is set, it will crush your throughput, as only one request will be processed per scan (Comms) or per certain control flow instructions (MSG). Be aware that if throttled with those settings, unthrottling will impact PLC scan time. Otherwise, there's not much you can do other than reduce the number of tags monitored. ---
**Author:** ![pgmo](https://avatars.discourse-cdn.com/v4/letter/p/d07c76/32.png) [@pgmo](https://forum.inductiveautomation.com/u/pgmo)\ **Post date:** [September 16, 2026, 12:45pm UTC](https://forum.inductiveautomation.com/t/allen-bradley-slc-communication-overload/117096/4 "2026-09-16T12:45:00Z")
> [@pturmel](#): > > other than reduce the number of tags monitored Hi @pturmel , thanks for your hints. I cannot touch the PLC - old thing. I've just tried increasing the tag group rate to 10.000 and overloading is gone - tags are temperature values and the customer is happy with a larger scan rate too. ---
**Author:** ![Nol](https://avatars.discourse-cdn.com/v4/letter/n/8e8cbc/32.png) [@Nol](https://forum.inductiveautomation.com/u/Nol)\ **Post date:** [September 16, 2026, 2:10pm UTC](https://forum.inductiveautomation.com/t/allen-bradley-slc-communication-overload/117096/5 "2026-09-16T14:10:36Z")
You could consider two scan groups, one for slow information that rarely changes (alarm set points, ranges, etc) and then one faster group for your realtime data. That way you can have better updates but lessen the load on the PLC/Network ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [September 16, 2026, 2:36pm UTC](https://forum.inductiveautomation.com/t/allen-bradley-slc-communication-overload/117096/6 "2026-09-16T14:36:07Z")
> [@pgmo](#): > > I cannot touch the PLC The settings I mention in the other thread are writable from Ignition. No other access to the PLC is requiired.