Hi...

I/O Intensive means, the Read Write process of the Oracle Datafiles in HDD, you can monitor this activity by using OS utility, if it is in Unix u can use IOSTAT, find out which HDD is having IO process, then look at the contents of the hdd, after that you can try to spread the contents to another HDD to give load ballancing and faster response to the application, this is part of The Oracle Performance Tuning...

TIA
Jeram
Oracle DBA