Library /sys$common/syshlp/nclhelp.hlb set, loopback_application  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    set  [node node-id] loopback application -
           maximum mirrors integer

    Example:

    set loopback application maximum mirrors 10

    Maximum Mirrors is an integer (0-4294967295) specifying the
    maximum number of loop mirrors supported.  The default value
    of 0 means the node supports an unlimited number of mirrors.

    For Tru64 UNIX to limit the number of loop mirrors, use the
    maximum instances characteristic of the session control application
    mirror entity.