VMS Help CMS, DELETE, GENERATION, Qualifiers, /GENERATION[=generation-expression]  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies a particular generation of the element to be deleted. By
    default, the most recent generation on the main line of descent is
    deleted. You cannot combine /GENERATION with any of the following
    qualifiers: /FROM, /TO, /AFTER, and /BEFORE.