Why can't I drop this Oracle datafile - even though it seems empty? This system is Oracle 11.2.0.3.0, using ASM.  We had an issue where there seemed to be a corruption issue of some kind - every time a row tried to get inserted into the table, we'd get the following:

ORA-01115: IO error reading block from file  (block # )
ORA-01110: data file 23: '&lt;filepath&gt;'
ORA-15081: failed to submit an I/O operation to a disk


Luckily, this is a test system and there happened to be only one table on data file 23, according to dba_extents.  I had the team drop the table and recreate it in another tablespace for the moment.

However, now I'd like to drop the datafile that was reporting the issue.
select count(*) from Dba_Extents where file_id = 23; reports 0 - so there seem to be no extents using that data file.  However, ALTER TABLESPACE tablespaceName DROP DATAFILE '&lt;filepath&gt;'; doesn't work.  I get the following:

Error report -
SQL Error: ORA-03262: the file is non-empty
03262. 00000 -  "the file is non-empty"
*Cause:    Trying to drop a non-empty datafile
*Action:   Cannot drop a non empty datafile


How can I drop this file?
Oracle here warn you from dropping datafile because it contain amount of data, to make sure the datafile is completely  empty please execute the following command

col tablespace_name format A30 heading tablespace
col file_name format A40
col tot_KB format 99,999,999
col tot_freeKB format  9,999,999
col Kb_max format  9,999,999

select f.tablespace_name
      ,f.file_name
      ,f.bytes/1024 tot_KB
      ,sum(nvl(s.bytes,0)/1024) tot_freeKB
      ,max(nvl(s.bytes,0)/1024) maxextent_freeKB
      ,( (sum(nvl(s.bytes,0)/1024)) / (f.bytes/1024) )*100 Pct_available
from   sys.dba_data_files f
      ,sys.dba_free_space s
where  f.file_id = s.file_id(+)
group by f.tablespace_name, f.file_name, f.bytes/1024
order by 1,2
;


if the datafile is completely empty, then you have one of the two option:

1) reboot the database ( sometime it help)

2) move all the data from one tablespace to another one, then drop the tablespace and rename the new one