How to monitor I/O bottle necks ?

Hi ,
I am an Oracle DBA. My database is on HP-UX 11.23. Our production system are experiencing huge performance problems recently. I know that the performance problems are due to amount of I/O done on some files. Is there any way to find out which files are being written into or read most often at Unix Level.

Any help is appreciated.

Thanks,
Vikings...

Don't know how to do this at unix level. Not available from "sar", "top" or "glance".

Easy in Oracle 9 with sqlplus:

select substr(name,1,50) name,phyrds,phywrts
from v$datafile a,v$filestat b
where a.file# = b.file#;