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

 astadr

    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       call without stack unwinding
    mechanism:    by 32- or 64-bit reference (Alpha)
    mechanism:    by 32-bit reference (VAX)
    AST service routine to be executed. On Alpha systems, the astadr
    argument is the 32- or 64-bit address of this routine. On VAX
    systems, the astadr argument is the 32-bit address of this
    routine.

 astprm

    OpenVMS usage:user_arg
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by 64-bit value (Alpha)
    mechanism:    by 32-bit value (VAX)
    AST parameter to be passed to the AST routine specified by the
    astadr argument. On Alpha sytems, the astprm argument is a
    quadword value containing this parameter. On VAX systems, the
    astprm argument is a longword value containing this parameter.

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode for which the AST is to be declared. The most
    privileged access mode used is the access mode of the caller. The
    resultant mode is the access mode for which the AST is declared.