VMS Help CMS, SHOW, GENERATION, Command Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 element-expression

    Specifies one or more elements. For each element, CMS lists the
    transaction record of the most recent generation on the main line
    of descent. If you do not supply an element expression, CMS lists
    a transaction record for each element in the library. An element
    expression can be an element name, a group name, a wildcard
    expression, or a list of these separated by commas.