DECLARE 
  v_data_xml CLOB; 
  v_clob_upd_sql CLOB; 
  v_bool BOOLEAN := false; 
  LV_OUT_XML XMLTYPE; 
  lv_number_of_nodes number := 2426; -- Number of nodes in XML
BEGIN 
 
 -- Variable holding the data XML  
  v_data_xml := q'[<?xml version="1.0" encoding="UTF-8"?>    
                  <myspace:datapacket                    
                  xmlns:html="http://www.w3.org/1999/xhtml"                    
                  xmlns:myspace="http://www.mywrb.com/test/myspace">      
                  <myspace:data>     
                  <myspace:sec>     
                  ]'; 
  FOR I IN 1..lv_number_of_nodes 
  LOOP 
    dbms_lob.append(v_data_xml,'<myspace:row><myspace:pk'||i||'>'||i||'</myspace:pk'||i||'></myspace:row>'); 
  END LOOP; 
  DBMS_LOb.APPEND(v_data_xml,'</myspace:sec></myspace:data></myspace:datapacket>'); 
   
  -- XMLQUERY to update all the nodes in the data XML  
    V_CLOB_UPD_SQL := 'declare default element namespace "http://www.mywrb.com/test/myspace";  (: :) '  
                    ||' copy $tmp := $inxml modify ('; 
  FOR i IN 1..lv_number_of_nodes 
  LOOP 
    IF v_bool THEN 
      dbms_lob.append(v_clob_upd_sql,','); 
    END IF; 
    DBMS_LOB.APPEND(v_clob_upd_sql,'(for $i in $tmp/datapacket/data/sec/row/pk'||I  
                                     ||' return replace value of node $i with "' 
                                     ||TO_CHAR(i+1)||'")'); 
    V_BOOL := TRUE; 
  END LOOP; 
  DBMS_LOB.APPEND(V_CLOB_UPD_SQL,') return $tmp'); 
   
  SELECT xmlquery( v_clob_upd_sql passing xmltype(v_data_xml) AS "inxml" returning content) 
  INTO lv_out_xml 
  FROM dual; 
END;