ORA-03297 file contains used data beyond requested RESIZE value

select

a.file_name,

a.bytes file_size_in_bytes,

(c.block_id+(c.blocks-1)) * &_BLOCK_SIZE HWM_BYTES,

a.bytes - ((c.block_id+(c.blocks-1)) * &_BLOCK_SIZE) SAVING

from dba_data_files a,

(select file_id,max(block_id) maximum

from dba_extents

group by file_id) b,

dba_extents c

where a.file_id = b.file_id

and c.file_id = b.file_id

and c.block_id = b.maximum

and c.tablespace_name = 'INDX'

ALTER DATABASE DATAFILE 'D:\lard1213\INDEX01.ORA' RESIZE 20000M;