select ( 1 -(sum(getmisses)/sum(gets)+sum(getmisses))))* 100  AS  "Hit rate" 
FROM v_rowcache

 19 - 26  Oracle8i Tuning

SELECT NAME, VALUE
FROM V$SYSSTAT
WHERE NAME IN (’DB BLOCK GETS’, ’CONSISTENT GETS’,
’PHYSICAL READS’);

Tuning the Buffer Cache
The output of this query might look like this:

NAME VALUE
 ------------------------------------------------------ ----------
 
DB BLOCK GETS  85792 
CONSISTENT GETS  278888 
PHYSICAL READS  23182 

Calculate the hit ratio for the buffer cache with this formula:
Hit Ratio =  1  - (physical reads / (db block gets + consistent gets))
Based on the statistics obtained by the example query, the buffer cache hit ratio is
 94 %.