The following restrictions apply when adding constraints to a file or table. The file:
Referential and check constraints have four states:
Defined means the constraint definition has been added to the file, but not all of the pieces of the file are there for enforcement. For example, the file's member does not exist.
Established means the constraint definition has been added to the file, and all of the pieces of the file are there for enforcement.
Enabled means the check constraint will be enforced if the constraint is also established. If the constraint is defined, then the file member structures do not yet exist for enforcement.
Disabled means the constraint definition will not be enforced, regardless of whether the constraint is established or defined.
To define or establish a referential constraint, the parent file and the dependent file must exist. However, if the parent or dependent file has no members, the constraint is defined only (not established).
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