Top 10 Memory Abusers

The following query will show the top 10 SQL statements using memory as a percentage of the entire system.

SQL> select sum(pct_bufgets)
from ( select rank() over ( order by buffer_gets desc ) as rank_bufgets,
to_char(100 * ratio_to_report(buffer_gets) 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