I am not able to create a joined logical file in a Synon/2E model. I downloaded the instruction from the link provided https://support.broadcom.com/web/ecx/solutiondetails?aparNo=CQ062843&os=AS400, but the instructions have been removed.
Release : 8.7
This functionality has been consolidated into the techdocs (see the resolution section below for the document) and the "Create a join file" procedure can be achieved by creating Virtual Fields.
Please make sure you are accessing the model using mode since creating Virtual Fields is a database creation function. Also, if the model file is in use by other users, the process can cause File locks. Perform the SHIFT + F10 on the "EDIT DATABASE RELATIONS" screen and this takes you to the "DISPLAY FILE LOCKS" screen. Review the Job and user details that are locking the file and request the identified user to exit the model and then try to use the file.