Any idea why HASH_JOIN is being done in serial mode ?

Question

Hi Guys,
I have a doubt. Although both my table and index are built with parallel degree of 8, i am wondering why the hash_join goes serially. Any idea ? The query seems to run very quickly ( In 10 mins ) until the Table and index fast full scan but it later crawls with hash join.
Some of you may be thinking that this is due to sort_area_size but i have 200 MB allocated per session. Hash_Area_size will obviously be double to that of sort_areasize.
The query is :
SELECT /*+ FULL (CU10) */
      CU10.XCM_CONSUMER_PK,
   CU10.COUNTRY_ISO3_C,
   CU10.CUCON_CNTCT_ST_S,
   CV01.VIN_ID_C
FROM
   XCM_CU10_CONTACT  CU10,
   XCM_CV01_CONS_VEH CV01
WHERE   
   (CU10.CUCON_CNTCT_ST_S BETWEEN '01-Jan-04' AND SYSDATE) AND
   CU10.COUNTRY_ISO3_C = CV01.COUNTRY_ISO3_C AND
   CU10.XCM_CONSUMER_PK = CV01.XCM_CONSUMER_PK AND
   CV01.CVEH_LINK_START_Y BETWEEN CU10.CUCON_CNTCT_ST_S AND CU10.CUCON_CNTCT_ST_S+183 AND
   CV01.VIN_TYPE_C = 'A';The plan is as below :
Operation     Object Name     Rows     Bytes     Cost     Object Node     In/Out     PStart     PStop
SELECT STATEMENT Optimizer Mode=ALL_ROWS          1           9592                     
FILTER                         :Q429700000     PCWC           
PARTITION RANGE ALL                         :Q429700000     PCWP      1     8
HASH JOIN          1      68      9592      :Q429700000     P->S      QC (RANDOM)      
TABLE ACCESS FULL     XCM_CU10_CONTACT     12 K     263 K     9580      :Q429700000     PCWP      1     8
INDEX FAST FULL SCAN     XCM_CV01_IDX_TOUCHPOINT     3 M     158 M     1      :Q429700000     PCWP      1     8
Your expert views are highly solicited. Thanks in advance.
Ganesh

Answer 1

Why do the hash_joins are not done in parallel. I thought it was due to the distinct clause but that doesn't seem to be the case.
I shall wait to hear from you.
BTW, table CU10 has 70 million rows and table CV01 has about 50 million rows
Regards,
Ganesh