Referential integrity enforcement

The input/output (I/O) access for files that are associated with established and enabled constraints varies. It depends on whether the file contains the parent key or foreign key in the constraint relationship. The system enforces referential integrity enforcement on all parent and dependent file I/O requests.

The database enforces constraint rules for all I/O requests whether from application programs or system commands (such as the Initialize Physical File Member (INZPFM) command) or SQL statements or file I/O utilities (such as STRSEU).

• Foreign key enforcement
  The delete and update rules that you specify when you create a constraint apply to parent key changes. The database enforces a no-action rule on the insert and update operations to the foreign key in order to maintain referential integrity. The system enforces this rule on the insert and update operations to the foreign key to ensure that the value of every non-null foreign key matches the value of the parent key.
• 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.