I’m looking for some guidance on how to narrow in on the cause for Transaction Groups to regularly take much longer than normal to execute. Some details:
- OPC data mode: Read. Timer values distributed at 204, 210, 214, 218 milliseconds
- All transaction groups are Stored Procedure groups using Microsoft SQL Server
- PLC is AllenBradley ControlLogix 1756-L83ES, MSG (Class 3) Utilization typically around 70%
- Ignition v7.9.14, CPU utilization at 2 to 4%
- There are 201 running Transaction Groups
I see 5 possible areas to go after:
- Detecting trigger
- Reading Input OPC items
- Executing SQL Stored Procedure
- Writing Output OPC items
- Gateway computer resources
A “normal” execution is about 400 ms in the PLC and Designer shows Last duration of around 0.18 seconds. Occasionally, I do see a longer Last duration in Designer, but usually it is long duration on the PLC, 2-6 seconds, and still shows as 0.18 seconds in Designer. That makes me suspect the trigger detection or threading on the Gateway.
Is it possible to turn on some additional logging to narrow in on the bottleneck?
Any other suggestions or areas to investigate?