How to identify "bad" index after analyze table validate structure cascade - from rdba or seg/obj.

Do this.

SELECT dbms_utility.data_block_address_file(to_number(trim(leading '0' from replace('&&rdba','0x','')),'XXXXXXXX')) AS rfile#,dbms_utility.data_block_address_block(
to_number(trim(leading '0' from replace('&&rdba','0x','')),'XXXXXXXX')) AS block# FROM dual;
    RFILE#     BLOCK#
---------- ----------
        20      17036

select segment_name, owner from dba_extents where file_id=20 and 17036 between block_id and block_id+blocks-1;


or

SQL> analyze table test validate structure cascade;
analyze table test validate structure cascade
*
ERROR at line 1:
ORA-01499: table/index cross reference failure - see trace file 

The associated trace file contains:

Table/Index row count mismatch
table 6559 : index 10000, 0
Index root = tsn: 6 rdba: 0x01400091

It means: A table scan returned 6559 rows and an index scan returned 10000 rows.

"Index root" is the segment header information for the index:

rdba: 0x01400091 is the Index segment header relative data block address. It is decimal 20971665 which is Rfile#=5 Block#=145 :

SQL> select dbms_utility.data_block_address_file(20971665)  "Rfile#"  
2          ,dbms_utility.data_block_address_block(20971665) "Block#"  
3 from dual;  

Rfile#     Block#  
---------- ----------  
5          145  

Running the next query can identify the associated index:

QUERY 1: 

SQL> select owner, segment_name, segment_type 
2    from  dba_segments 
3    where header_file = 5 
4      and header_block = 145; 

OWNER    SEGMENT_NAME    SEGMENT_TYPE 
-------- --------------- ------------------ 
SCOTT    I_TEST          INDEX