/sys$common/syshlp/helplib.hlb System Services, $DCLCMH, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 addres

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Routine to receive control when a change mode trap or a
    compatibility mode fault occurs. The addres argument is the
    exception handling code in the address space of the calling
    process.

    If you specify the addres argument as 0, $DCLCMH clears the
    previously declared handler.

 prvhnd

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Address of a previously declared handler. The prvhnd argument
    is the address of a longword containing the address of the
    previously declared handler.

 type

    OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Handler type indicator. The type argument is a longword value.
    The value 0 (the default) indicates that a change mode handler
    is to be declared for the access mode at which the request is
    issued; the value 1 specifies that a compatibility mode handler
    is to be declared.