request_id

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Request identifier supplied by the symbiont to the user routine
    currently calling PSM$READ_ITEM_DX. The symbiont always supplies
    a request identifier when it calls a user routine with a service
    request. The request_id argument is the address of a longword
    containing this request identifier value.

    Your user routine must copy the request identifier value that the
    symbiont supplies (in the request_id argument) when it calls your
    user routine. Then, when your user routine calls PSM$READ_ITEM_
    DX, it must supply (in the request_id argument) the address of
    the request identifier value that it copied.

 item

    OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Item code that identifies the message item that PSM$READ_ITEM_DX
    is to return. The item argument is the address of a longword that
    specifies the item's code.

 buffer

    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor
    Buffer into which PSM$READ_ITEM_DX returns the specified
    informational item. The buffer argument is the address of a
    descriptor pointing to this buffer.

    The PSM$READ_ITEM_DX routine returns the specified informational
    item by copying that item to the buffer using one of the
    STR$COPY_xx routines documented in the OpenVMS RTL String
    Manipulation (STR$) Manual.