Shrink a datafile, when ALTER TABLESPACE COALESCE is not working.

In a 11.2.0.3 database, we tried to reclaim space from USERS tablespace.
We faced a problem.
We use the following query to the the end of a particular USERS' datafile [file_id=72, filename=/oradb/SBLCCPRD/oradata4/users03.dbf]

SELECT
        A.FILE_ID,
        A.BLOCK_ID,
        A.BLOCK_ID + A.BLOCKS - 1   END_BLOCK,
        A.BLOCKS,
        --ROUND(A.BLOCKS*B.BLOCK_SIZE/1024/1024,2) MBYTES,
        A.BLOCKS*B.BLOCK_SIZE "SIZE",
        A.OWNER,
        A.SEGMENT_NAME,
        A.PARTITION_NAME,
        A.SEGMENT_TYPE
    FROM
        DBA_EXTENTS A, DBA_TABLESPACES B
    WHERE
        A.FILE_ID=:A AND A.TABLESPACE_NAME=B.TABLESPACE_NAME
UNION ALL
SELECT
        A.FILE_ID,
        A.BLOCK_ID,
        A.BLOCK_ID + A.BLOCKS - 1   END_BLOCK,
        A.BLOCKS,
        --ROUND(A.BLOCKS*B.BLOCK_SIZE/1024/1024,2) MBYTES,
        A.BLOCKS*B.BLOCK_SIZE "SIZE",
        'free'          OWNER,
        'free'          SEGMENT_NAME,
        NULL            PARTITION_NAME,
        NULL            SEGMENT_TYPE
    FROM
        DBA_FREE_SPACE A, DBA_TABLESPACES B
    WHERE
        A.FILE_ID=:A AND A.TABLESPACE_NAME=B.TABLESPACE_NAME
    ORDER BY 2 DESC;

We can see there were 5 contiguous free extents of 64 Kbytes each, total 320 Kbytes.

   

FILE_ID	BLOCK_ID	END_BLOCK	BLOCKS	SIZE	OWNER	SEGMENT_NAME	PARTITION_NAME	SEGMENT_TYPE
72	1614952	1614959	8	65536	free	free
72	1614944	1614951	8	65536	free	free
72	1614936	1614943	8	65536	free	free
72	1614928	1614935	8	65536	free	free
72	1614920	1614927	8	65536	free	free
72	1614912	1614919	8	65536	AMARGARI	CX_OTE_LOV_BACKUP_06052014		TABLE
72	1614904	1614911	8	65536	AMARGARI	CX_OTE_LOV_BACKUP_06052014		TABLE
72	1614896	1614903	8	65536	EFOTEINOP	CX_OTE_LOV_0106		TABLE
...	...	...	...	...	...	...	...	...

We tried to coalesce the tablespace, but it did not. The free extents did not get merged to one of 320 Kbytes.

SQL> alter tablespace users coalesce;
Tablespace altered. 

This is the datafile's size in bytes:

SELECT FILE_NAME, BYTES
FROM DBA_DATA_FILES
WHERE FILE_ID=72;

FILE_NAME	BYTES
/oradb/SBLCCPRD/oradata4/users03.dbf	13229744128

When we tried to shrink the datafile, even by just 8 Kbytes, we got ORA-03297:

SQL> ALTER DATABASE DATAFILE 72 RESIZE 13229735936;
ALTER DATABASE DATAFILE 72 RESIZE 13229735936
*
ERROR at line 1:
ORA-03297: file contains used data beyond requested RESIZE value

The solution was to purge the tablespace's recycle bin, even if there were no recycled objects near the end of the datafile. Furthermore, before I begin all this procedure, I had purged the database's recycle bin, using "PURGE DBA_RECYCLEBIN".

SQL> PURGE TABLESPACE USERS;
Tablespace purged.

SQL> ALTER DATABASE DATAFILE 72 RESIZE 13229735936;
Database altered.

   

FILE_ID	BLOCK_ID	END_BLOCK	BLOCKS	SIZE	OWNER	SEGMENT_NAME	PARTITION_NAME	SEGMENT_TYPE
72	1614920	1614951	32	262144	free	free
72	1614912	1614919	8	65536	AMARGARI	CX_OTE_LOV_BACKUP_06052014		TABLE
72	1614904	1614911	8	65536	AMARGARI	CX_OTE_LOV_BACKUP_06052014		TABLE
72	1614896	1614903	8	65536	EFOTEINOP	CX_OTE_LOV_0106		TABLE
...	...	...	...	...	...	...	...	...