Poor Performance Data Refresh

[sinced]

I am facing some performance issues with the data actualization on a process display screen. There are many tags on the process displays and sometimes it can take up to 12 second to get data refreshed and correctly displayed.

Aveva Plant Scada Version: 2023 R2

Server Operating System: Windows 11

Server SSD: 500GB

Server RAM: 16GB

Server Processor: 12th Gen Intel Core i5-12500T (12 CPUs), 2Ghz.

The same hardware configuration is applicable for the unique client machine.

[olivier_vallee]

Hi @sinced 

I'd recommend reaching out to AVEVA or Schneider technical support to troubleshoot this issue.

Things I'd be looking at if I were trying to debug this system:

- Take a look at syslog.dat and IOServer_Syslog.dat for any indication of interruptions

- Look at machine resources (is memory or CPU high, any specific processes consuming a lot of CPU?)

- Is antivirus running, has it been configured to exclude Plant SCADA data directories?

- What protocol or drivers are being used in the project? Any bottlenecks or timeouts? Any devices offline?

Wish you all the best.

Kind regards

Olivier

[sinced]

The poor performance is due to the Modbus TCP Driver. The PLCs are M580 type and the Modbus TCP Driver was used. However due to the various addresses to not located within the same range, the IOServer is struggling to read all the tags in a real time. The solution is to change the IO acquisition from Modbus TCP to OFS. OFS can read tags via the Data Dictionnary and Citect will just update the database through the OPC Link. Data read by OFS are based on the symbolic variable names not through Device Addresses that is the reason why it is more performant. 

[olivier_vallee]

Hi @sinced 

Thanks for the feedback.

One major difference between MODNET (Modbus on TCP) and OFS (Modbus "Extended") is the packet size. With the standard Modbus, it is 256 bytes, but with Modbus "Extended" (via OFS) it is capable of 1024 bytes. So about 4x larger payload size.

But that is not to say that MODNET could not be capable of fullfilling your system requirements. There are a number of changes that can be made to improve performance throughput. Namely:

- Adjust MODNET parameters MaxPending and MaxOutstanding from default (some trial and error to see what works best)

- Depending on PLC hardware, some comms modules have greater communications throughput performance, so it might be possible to switch comms config to get better throughput

Kind regards

Olivier