Why only Query Co-ordinator process CLOB with Parallel query?

 Hi All,

I'm currently query a big table with clob, and run sql like this:

Set linesize 132 pagesize 1000
Set timing on time on autotrace traceonly
Set arraysize 1000
SELECT   /*+parallel_index(TABLE_WITH_LOB, TABLE_WITH_LOB_IX1,8) parallel_index(TABLE_WITH_LOB, TABLE_WITH_LOB_IX2,8)*/
 ITEM_ID
,CLOB_INFO
,CREATION_DATE
,LAST_MODIFIED_DATE
FROM
TABLE_WITH_LOB
WHERE LOB_TYPE = 1
AND
((LAST_MODIFIED_DATE >=
to_date('2010-11-12 12:00:00' , 'yyyy-mm-dd hh24:mi:ss')
AND LAST_MODIFIED_DATE < to_date('2010-11-12 18:00:00' , 'yyyy-mm-dd hh24:mi:ss'))
OR
(CREATION_DATE >= to_date('2010-11-12 12:00:00' , 'yyyy-mm-dd hh24:mi:ss')