Interestingly, with reference to:

"Spinning in memory is relatively rare and can be constructed with
Connor McDonald's sinister "hit ratio adjusting tool" but I didn't see
to many of it in real life."

In my experience, its all too common... in particular queries to dual
- heaps and heaps of

select user from dual
select sysdate from dual
select <sequence>.nextval from dual
select <simple expression> from dual

dual...dual....dual....dual....dual.....aarrrggghhh!

closely followed by:

select <description>
from  <generic_application_wide_reference_lookup_table>
where domain = ...
and   surrogate_key = ...



--
Connor McDonald
===========================
email: connor_mcdonald@(protected)
web:  http://www.oracledba.co.uk

"Semper in excremento, sole profundum qui variat"
--
http://www.freelists.org/webpage/oracle-l