Hit ratio question

I have a severe performance problem, the hit ratio as calculated by Method-1:
(1 - (physical rds/logical rds))*100 is about 15%
However, when i calculate hit ratio on a per user basis using the following logic:
Method -2
(1 - (physical rds/logical rds))*100

where v$session.sid=v$sess_io.sid
and username is not null
and (consistent_gets + block_gets) > 0

        i get hit ratio of near 100% for all users. To be more precise, No.of physicalreads is high in method -1 and near zero in method -2.

Could somebody help me understand this please.

Appreciate if you could send a mail!

Thanks,
Nat. Received on Mon Feb 09 1998 - 00:00:00 CST