Two systems are used as Primary and standby system (redundant HMI).

All things are right only sometimes (once per 40-45 seconds) I have #COM in each tag for 2 or 3 seconds and then the data are shown valid.
I checked all setting and they are OK.

Of course when primary system is shutdown, the tags of stand by system became #COM and after about 4-5 minutes, the tags take valid data and HMI shows correct data

 

Sounds like you are having a similar problem to myself. Seems that changing the Integrity polling can fix this. Seems both systems will "hog" the RTU comms while they negotiate who is primary master, and who is standby.

 

What is the version of your CitectSCADA?

What kind of communication and PLC in you are using in project?

Provide us with as much details as would help to understand your configuration.

 

Can you force a General Interrogation on your RTU (GI) normally drivers do this on startup. Which RTU Vendor is it?

How does the system behave when only the primary IO Server is online, and primary is off at startup? do you still get the #COM?

Might be worth posting sections of your citect.ini.

You could write a cicode task to check for IsIOServerOnline() using IODevice()calls, and if it changes from FALSE to TRUE send a GI to the RTU to force refresh of data, this should minimise the #COM when the Secondary takes over.

Are you using Modems? or straight com ports? I'd check with citect as there have been many a known issue with modems dropping out for no apparent reason.

Ian Finlay
www.earthed.com
Freelance Citect/C++/VB/C#/.NET