Tablespace shrinking

iam using oracle 9i R2 and i want to reduce my datafile size but it's show's that error when i try to resize it. ORA-03297

If you try to resize a datafile to a size smaller than is needed to contain all
the database objects in that datafile, you will get an error:

ORA-03297: file contains <number> blocks of data beyond requested
RESIZE value

Hi,

We can directly resize datafiles

1.TEST.SQL>SELECT FILE_NAME, BYTES FROM DBA_DATA_FILES WHERE TABLESPACE_NAME='SYSTEM';

FILE_NAME

     BYTES

/.../dbsGNX.dbf

 419430400

2.TEST.SQL>ALTER DATABASE DATAFILE '/.../dbsGNX.dbf' RESIZE 390M;
Database altered.
Or Error

ORA-03297: file contains <number> blocks of data beyond requested
RESIZE value

3.TEST.SQL>SELECT FILE_NAME, BYTES FROM DBA_DATA_FILES WHERE TABLESPACE_NAME='SYSTEM';

FILE_NAME

     BYTES

/.../dbsGNX.dbf

 408944640

But the minimum file size is the size of the extend the furthest in the datafile:

4.TEST.SQL>SELECT FILE_ID,FILE_NAME FROM DBA_DATA_FILES WHERE TABLESPACE_NAME='SYSTEM';

   FILE_ID

FILE_NAME

         1

/.../dbsGNX.dbf

5.TEST.SQL>SELECT MAX(BLOCK_ID) MBID FROM DBA_EXTENTS WHERE FILE_ID=1;

      MBID

     25129

6.TEST.SQL>SELECT SEGMENT_NAME,OWNER,SEGMENT_TYPE FROM DBA_EXTENTS WHERE FILE_ID=1 AND BLOCK_ID=25129;

SEGMENT_NAME                                                                      OWNER                          SEGMENT_TYPE

------------------------------

I_OBJAUTH2                                                                        SYS                            INDEX

7.TEST.SQL>SHOW PARAMETER BLOCK_SIZE

NAME                                 TYPE                             VALUE

--------------------------------

db_block_size                        integer                          8192

8.TEST.SQL>SELECT 8192*25129 FROM DUAL;

8192*25129

 205856768

about 200M.