Parent key enforcement

The rules that you specify for the referential constraint determine how the database processes the delete and update operations on the parent key. The system enforces the unique attribute of a parent key on all parent file I/O.

• Enforcement of delete rules
  When you delete a record from a parent file, the system checks the dependent file for any dependent records (matching non-null foreign key values). If the system finds any dependent records, the delete rule determines the action that is taken.
• Enforcement of update rules
  When the system updates a parent key in a parent file, it checks for any dependent records (matching non-null foreign values) in the dependent file. If it finds any dependent records, the update rule for the constraint relationship determines the action that it takes.