SQL & PL/SQL

Hi,

Please help folks to optimize this query below where error I am getting is: ORA-19011: Character string buffer too small

SELECT pla.attribute1,  IMP.ORGANIZATION_ID,IMP.ORGANIZATION_code, SUM(plla.QUANTITY - plla.QUANTITY_RECEIVED) TO_SUMM,

(RTRIM (XMLAGG (XMLELEMENT (E, ' PO#'||pha.segment1 || '(' || IMP.ORGANIZATION_code || ')_'||plla.promised_date|| '_'|| (pla.line_num|| '.'|| plla.shipment_num|| ' x  QTY Due: '||(plla.QUANTITY - plla.QUANTITY_RECEIVED))

                   || ', ')ORDER BY plla.promised_date).EXTRACT (' //text()'), ', ') )  "ITEM_SUPP" --- pla.item_id

                   FROM po.po_line_locations_all plla,

          po.po_lines_all pla,

          po.po_headers_all pha,

          inv.MTL_PARAMETERS IMP

    WHERE     plla.closed_code = 'OPEN'

          AND plla.po_header_id = pha.po_header_id

          AND plla.po_line_id = pla.po_line_id

          AND pla.attribute1 IS NOT NULL         

          AND plla.SHIP_TO_ORGANIZATION_ID = IMP.ORGANIZATION_ID(+)

GROUP BY pla.attribute1, IMP.ORGANIZATION_ID,IMP.ORGANIZATION_code

ORDER BY IMP.ORGANIZATION_ID,  pla.attribute1

Thanks.