Why the query is not using index in Oracle?

Why the query is not using index in a client's environment? We tested the query and it used indexes (see the explain plan). But it does full table scan in our client's machine.


Our environment: Oracle 9.2.0.8 on Window server
Clinet's environment: Oracle 9.2.0.8 on Unix server

We have asked the client to dump the schema and imported the dumped schema to our environment. It uses indexes. I asked the client to send me fragmentation info. There is only 130 fragments in the tablespace.

Any clue what it might cause the problem?


SELECT
    C.DOCUMENT_SUBTYPE_ID AS DOCUMENT_SUBTYPE_ID,
    DNAME.NAME AS CAT_NAME,
    SUM(C.PAGE_COUNT) AS PAGE_COUNT,
    SUM(C.BOOKMARK_COUNT) AS BOOKMARK_COUNT,
    SUM(C.HYPERLINK_COUNT) AS HYPERLINK_COUNT,
    SUM(C.VARIABLE_COUNT) AS VARIABLE_COUNT,
    COUNT(*) AS TOTAL_DOCS
FROM CONTAINER C
    INNER JOIN I18N DNAME ON (DNAME.PARENT_OBJECT_ID=C.DOCUMENT_SUBTYPE_ID AND DNAME.LOCALE_CODE = 'en_US')
    INNER JOIN CONTAINER_CONTENT_OBJECT CCO ON (CCO.CONTAINER_ID = C.OBJECT_ID)
    INNER JOIN CONTENT_OBJECT CO ON (CCO.CONTENT_OBJECT_ID = CO.OBJECT_ID)
    INNER JOIN CONTAINER_ANCESTOR CA ON C.OBJECT_ID = CA.CONTAINER_ID
WHERE C.DOCUMENT_YN = 'Y' AND CA.ANCESTOR_ID = 7208866 AND CCO.CURRENT_YN = 'Y'
GROUP BY C.DOCUMENT_SUBTYPE_ID,DNAME.NAME
ORDER BY COUNT(*) DESC

Plan
SELECT STATEMENT  CHOOSECost: 89  Bytes: 710  Cardinality: 10                                                  
      13 SORT ORDER BY  Cost: 89  Bytes: 710  Cardinality: 10                                            
            12 SORT GROUP BY  Cost: 89  Bytes: 710  Cardinality: 10                                      
                  11 NESTED LOOPS  Cost: 86  Bytes: 710  Cardinality: 10                                
                        9 NESTED LOOPS  Cost: 76  Bytes: 660  Cardinality: 10                          
                              7 NESTED LOOPS  Cost: 66  Bytes: 380  Cardinality: 10                    
                                    4 NESTED LOOPS  Cost: 24  Bytes: 567  Cardinality: 21              
                                          1 INDEX RANGE SCAN NON-UNIQUE WYETHQA.CONTAINER_ANCESTOR_AID_CID Cost: 3  Bytes: 210  Cardinality: 21        
                                          3 TABLE ACCESS BY INDEX ROWID WYETHQA.CONTAINER Cost: 1  Bytes: 17  Cardinality: 1        
                                                2 INDEX RANGE SCAN NON-UNIQUE WYETHQA.CONTAINER_OID_IDX Cardinality: 1  
                                    6 TABLE ACCESS BY INDEX ROWID WYETHQA.CONTAINER_CONTENT_OBJECT Cost: 2  Bytes: 11  Cardinality: 1              
                                          5 INDEX RANGE SCAN NON-UNIQUE WYETHQA.CONT_CONT_OBJ_CONT_ID_IDX Cost: 1  Cardinality: 1        
                              8 INDEX RANGE SCAN NON-UNIQUE WYETHQA.I18N_POI_LC_N Cost: 1  Bytes: 28  Cardinality: 1                    
                        10 INDEX RANGE SCAN NON-UNIQUE WYETHQA.CONTENT_OBJECT_OBJECT_ID_IDX Cost: 1  Bytes: 5  Cardinality: 1                          



=======================================================================================