Referential Integrity ensures that foreign keys correctly map to primary keys. A referential constraint prevents the insertion or update of foreign keys for which there are no matching primary keys. It either prevents the deletion of primary keys if foreign keys exist, or deletes these foreign rows (DELETE CASCADE).
SQL *net is the Oracle network interface that allows Oracle tools running on network workstations and servers to access, modify, share, and store data on other servers. SQL *net is considered part of the program interface in network communications.