Are there any circumstances where we would need to set up DB2 ODBC Initialization File on z/OS lpar to access a DB2 database on the same z/OS lpar?

For example, I have a database 'xxyyzzcc' on z/OS lpar 'aaaa' in the DB2 sub-system 'BBBB'. Will there be a circumstance where I would need to set up DB2 ODBC Initialization File on z/OS lpar 'aaaa' to access a DB2 database 'xxyyzzcc' on the same z/OS lpar 'aaaa' ?

sbsai