The script will create a report of reads,writes on your data files.
col PHYRDS format 99,999,999
col PHYWRTS format 99,999,999
ttitle "Disk Balancing Report"
col READTIM format 99,999,999
col WRITETIM format 99,999,999
col name format a30
select name, phyrds, phywrts, readtim, writetim
from v$filestat a, v$dbfile b
where a.file# = b.file#
order by readtim desc;