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

 o  maximum data

    Default: 4096

    The maximum size, in octets, of the loop message data field that
    the loop mirror can reflect. If the loop mirror receives a loop
    message with a longer data field, an error occurs. You cannot
    modify this characteristic.

 o  maximum mirrors

    Default: 0             Value: 0-4294967295

    Enter the maximum number of loop mirrors supported. If you enter
    the value 0, 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 mir (NOT
    MIRROR) entity.