If you want to make a Cobol system, write your system with flat files and use Cobol. Or C. The system will run much faster than using a database.
Here is an Oracle script to find the tables that don’t have any foreign keys.
Tables that are neither a parent table, or a child table.
After discovering so many tables that no primary key, at so many shops, I finally wrote an Oracle script to list all the tables that did not have a PK.