start_va_64

    OpenVMS usage:address
    type:         quadword address
    access:       read only
    mechanism:    by value
    Lowest address in range of addresses that express the stack's new
    limits. For a memory stack, this address is the stack limit. For
    an Integrity servers register stack, this address is the stack
    base.

 length_64

    OpenVMS usage:length
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by value
    Length of the range of addresses that express the stack's new
    limits.

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode of the stack to be altered. The acmode argument is
    a longword containing the access mode. The $PSLDEF macro defines
    symbols for the four access modes. The most privileged access
    mode used is the access mode of the caller.

    If acmode specifies user mode, $SETSTK_64 performs no operation
    and returns the SS$_NORMAL condition value.

 flags

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    0 for memory stack (Alpha and Integrity servers VA$M_SETSTK_
    REGISTER for register stack (Integrity servers only)

    The $VADEF macro and VADEF.H file define symbolic names for the
    flags argument.

 prev_start_va_64

    OpenVMS usage:address
    type:         quadword address
    access:       write only
    mechanism:    by reference
    Lowest address in the range of addresses that express the stack's
    previous limits. For a memory stack, this address was the stack
    limit. For an Integrity servers register stack, this address was
    the stack base.

 prev_length_64

    OpenVMS usage:length
    type:         quadword
    access:       write only
    mechanism:    by reference
    Length of the range of addresses that express the stack's
    previous limits.