Loss of Tags in SCADA After PLC Updates

[oualid]

Description:

Hello Support Team,

I am encountering an issue with our DCS system where we are losing tags in our SCADA system after making changes and uploading them to one of our PLCs. Here are the details of our setup and the issue:

System Configuration:

• OPC Server: Schneider OPC Factory Server
• SCADA Software: Vijeo Citect 2015
• Connection: Ethernet
• PLCs: 5 PLCs connected via Ethernet (PLC1 to PLC5)
• Machine Setup: The OPC server and SCADA are running on the same machine.

Issue Description:

Whenever I make changes to one of the PLCs (e.g., PLC1), and upload these changes to the PLC three times, we observe that some tags in the SCADA system corresponding to this PLC are lost. This issue is consistent and happens every time we follow this procedure.

Steps to Reproduce:

1. Make changes to PLC1.
2. Upload the changes to PLC1.
3. Repeat the upload process three times.
4. Observe the loss of some tags in Vijeo Citect 2015 SCADA.

[olivier_vallee]

Hi @oualid,

Wow, you have some vintage product versions in production! Any reason why you haven't updated them to take advantage of latest bug fixes and enhancements?

What I can say is that this is a known issue. Basically OFS and the PLC are out of sync when you make changes to the PLC tag database. This was resolved in OFS by allowing it to pre-load the updated Data Dictionary from the PLC before starting the new scan and implementating the PLC changes. 

See this forum post for the problem and recommended solution:

https://community.se.com/t5/Modicon-PAC-Forum/OFS-Server-Preloading-on-build-changes-program/td-p/26...

Basically upgrade to the latest OFS version 3.63 SP3, tick the options in OFS for "Using Data Dictionary" and "No Communications Break" to ensure there is no comms break between SCADA, OFS and the PLC. Of course if you modify a tag name in the PLC, you would also need to make the corresponding change to the Variable Tag Address to match.

[oualid]

Hi @olivier_vallee,

I am no responsable for the updated the product versions and no one here to do that, I would like to do that.
about the OFS options "Using Data Dictionary" and "No Communications Break" are ticked.
I followed the forum post provided from you, I find only the preload on build changes in the PLC project settings \ embedded data settings is not ticked, is that what you meant, about allowing the OFS to pre-load the updated Data Dictionary from the PLC before starting the new scan?

Thank you about your quick response.

[olivier_vallee · Accepted solution]

It has been quite some time since I used Unity Pro to program the PLC, but I believe there should be an option to create the data dictionary on build of the PLC program, which also gets stored in the PLC memory. Here is the Schneider FAQ which outlines the steps:

https://www.se.com/sg/en/faqs/FA384523/

[oualid]

Hi @olivier_vallee, thank you for your time and advice. I resolved the issue by generating a new XVM symbol table file after adding the new tags to the PLC program and replacing the old file with. This allowed the OFS to reconnect with the PLC successfully.

[olivier_vallee]

Thanks for the feedback. Please know that newer versions of OFS are capable of reading the Data Dictionary stored in the PLC (after it is updated) and provide a seamless solution with no interruption to communications or manual exporting files. But I'm glad to hear you are happy with the solution you found.