Top 10 Disk-Read Abusers

The following query will show the top 10 heaviest disk reading statements as a percentage of the entire system.

SQL> select sum(pct_bufgets)
from ( select rank() over ( order by disk_reads desc ) as rank_bufgets,
to_char(100 * ratio_to_report(disk_reads) over (), '999.99') pct_bufgets
from v$sqlarea )
where rank_bufgets < 11;

If the percentage is

< 5% then good performance
5 - 20% then average performance
>25% then bad performance

Thanks