A referential integrity constraint may be violated by: Deleting a referenced record. Updating the primary key of a referenced record Updating the foreign key of a referencing record all of the above Question 6 2 pts A catalog in a database system stores: The database files The database schema The database programs Question 7 2 pts In the three-tier client-server architecture, the database resides at bottom (senver) tier. middle (application) tier. top (client) tier