Foreign Keys

ORA-01031 Insufficient privileges

I am trying to generate FK on table in schema A, which is the reference of PK on another table in schema B. The owner of schema A is also a DBA. It gives an error ORA-01031 Insufficient privillages

Oracle Application Express Item

I have two tables with parent-child relationship. Is there a way to automatically populate the foreign key field of the child table with the exact data from the primary key of the parent table?