ORA-03297: file contains used data beyond requested RESIZE value

Cause : Some portion of datafile are using by database Segment which you trying to trim.

Solution : Move / Drop all Segment extends from the region prior that you want to trim.

SQL> ALTER DATABASE DATAFILE '/u01/app/oracle/oradata/orcln1/tbs_data01.dbf' RESIZE 1700M;
ALTER DATABASE DATAFILE '/u01/app/oracle/oradata/orcln1/tbs_data01.dbf' RESIZE 1700M
*
ERROR at line 1:
ORA-03297: file contains used data beyond requested RESIZE value

SQL> SELECT TABLESPACE_NAME
  2  FROM DBA_DATA_FILES
  3  WHERE FILE_NAME ='/u01/app/oracle/oradata/orcln1/tbs_data01.dbf';

TABLESPACE_NAME
------------------------------
TBS_DATA

SQL> SELECT DISTINCT SEGMENT_TYPE,SEGMENT_NAME
  2  FROM DBA_EXTENTS
  3  WHERE TABLESPACE_NAME = 'TBS_DATA';

SEGMENT_TYPE       SEGMENT_NAME
------------------ ---------------------------------------------------------------------------------
TABLE              TEST_RECLAIM_SPACE
INDEX              IND_SERIAL_NO_TEST_RECL

SQL> ALTER TABLE TEST_RECLAIM_SPACE MOVE;

Table altered.

SQL> ALTER INDEX IND_SERIAL_NO_TEST_RECL REBUILD TABLESPACE TBS_DATA;

Index altered.

SQL> purge recyclebin;

Recyclebin purged.

SQL> ALTER DATABASE DATAFILE '/u01/app/oracle/oradata/orcln1/tbs_data01.dbf' RESIZE 1700M;

Database altered.

SQL>