Is it bad idea to create foreign keys on the tables in a different schemas in the same database for big applications?
Schemas are nice to isolate tables from logical subsystems. Foreign keys guarantee data integrity. These are orthogonal concepts - as obviously data integrity between subsystems is also a must have. Accounting and Shipping and possibly Central Customer Data do not live in silos where a customer can get deleted while being used in accounting.
This is how I do it on SQL Server (although, again, our definition of schema is IIRC a LITTLE different from the Oracle definition).
As such, I think the requirement of the DBA is a sign of incompetence. T