Attempts to modify a back reference field from any IBM Rational ClearQuest client or when using the ClearQuest API results in the error "The field "Parent" cannot be modified because it is a back reference field.".
When you try to modify a back reference field, an error like the following might display:
The field "Parent" cannot be modified because it is a back reference field. This field is automatically updated when this entity is added or removed from the "Child" field of a "Defect" entity.
As of ClearQuest versions 188.8.131.52, 7.1.1.04, and 7.1.2.01, ClearQuest no longer lets you modify back reference fields because this type of modification can cause database corruption.
The problem can occur when a hook explicitly tries to modify a back reference field, or if a list view control is explicitly attached to a back reference field with the New, Add, or Delete button. As of ClearQuest versions 8.0.0.09 and 8.0.1.02, a back reference field is made to be ReadOnly so it cannot be modified through a user interface client or APIs (from a non-hook context).
The problem has not been observed when creating a back reference control by dragging and dropping the back reference field onto the form.
The error results from code changes applied to resolve APAR PM22186, ClearQuest core should be able to detect when a remove is taking place on a back reference field and throw an exception or no-op.
Resolving the problem
You can selectively enable the ability to modify a back reference field as a short-term work around until the schema can be changed to no longer rely on modifying a back reference field.
Contact IBM Software Support for guidance on how to do this.