Ensure data integrity with referential constraints

These topics discuss how to use referential constraints in your database to ensure that it contains only valid data.

You can use referential constraints in iSeries™ databases to enforce the referential integrity of your system. Referential integrity encompasses all of the mechanisms and techniques that you use to make sure that your database contains only valid data.

• Add referential constraints
  You can add referential constraints on physical files with no more than one member. A referential constraint is a file-level attribute; therefore, you can create the constraint before the member exists.
• Verify referential constraints
  The system automatically verifies the validity of a referential constraint when you add the constraint with the Add Physical File Constraint (ADDPFCST) command. The system verifies that every non-null value in the foreign key matches a corresponding value in the parent key.
• Enable or disable referential constraints
  You can enable or disable a referential constraint using the Change Physical File Constraint (CHGPFCST) command or iSeries Navigator.
• Remove referential constraints
  You can remove referential constraints in various ways. The full impact of the removal depends on the constraint you are removing and the certain conditions that surround the constraint.
• Details: Ensure data integrity with referential constraints
  You might want to use referential integrity in your database management system for several reasons.
• Example: Ensure data integrity with referential constraints
  Here is an example of how to ensure data integrity with referential constraints.
• Referential integrity terms
  A discussion of referential integrity requires an understanding of several terms. These terms are in an order that might help you understand their relationship to each other.
• 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.
• Constraint states
  A file can be in one of three constraint states. In two of the states, the constraint can be enabled or disabled.
• Check pending status in referential constraints
  Check pending is the condition of a constraint relationship when potential mismatches exist between parent and foreign keys. When the system determines that referential integrity might have been violated, the constraint relationship is marked as check pending.
• Referential integrity and CL commands
  Referential integrity affects the characteristics of some CL commands.