/sys$common/syshlp/helplib.hlb SET, FILE, Qualifiers, /VERSION_LIMIT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /VERSION_LIMIT[=n]

    Specifies the maximum number of versions for the specified file.
    If you do not specify a version limit, a value of 0 is used,
    indicating that the number of versions of a file is limited only
    to the Files-11 architectural limit of 32,767. When you exceed
    that limit, the earliest version of the file is deleted from
    the directory without notification to the user. For example, if
    you set the version limit to three when there are already five
    versions of that file in your directory, there will continue to
    be five versions of the file unless you specifically delete some
    or purge the directory. Once the number of versions is equal
    to or less than the current version limit, the version limit is
    maintained.