Applies To:
  • CitectSCADA 5.40 and above
  • CitectHMI 5.40 and above

I am using a tag-based driver (such as OPC or ABLOGIX) in a CitectSCADA system with at least two networked CitectSCADA PCs. The I/O Server displays all tag values correctly, but one or more other PCs display all tags values as 0. There are no errors on either CitectSCADA PC. 

This can happen if two projects have the same project ID number. When the project is compiled, CitectSCADA will give it a new project ID. The project ID is used to generate an OID number for each variable tag, so now all the tags in this copy of the project will have different OIDs than the server's project. Since the client uses OID numbers (not tag names) to read tags from the I/O server, it will be requesting OIDs that don't exist on the server. By design, 0 is returned for invalid OIDs.

To correct this, you need to have the same project ID on each copy of the project. To check or change the project ID, go to the Citect Explorer. Right-click on the project and choose Project Properties. Each PC that is running this project must use the same project ID.

See KB Article Q3657 for more information about OIDs and project IDs.