VMS Help CMS, REMOVE, GENERATION, Qualifiers, /IF_PRESENT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Directs CMS to remove any generation of the element that exists
    in the class. If the class does not contain a generation from the
    element, CMS takes no action and does not return an error. When
    you use wildcard characters in the element expression, /IF_PRESENT
    is the default.