Read Hit Ratio Question- Suggestions Welcome.

Hey Gurus,
 I am doing this query to find out the Read Hit ratios on a Baseline system (upon which further development will be done) .

select 1-(sum(decode(name, 'physical reads', value,0))/ 	


	 (sum(decode(name, 'db block gets', value,0)) + 	


	 (sum(decode(name, 'consistent gets', value,0))))) * 100


	 "Read Hit Ratio" 
from   v$sysstat;

 I am getting very weird results on about four systems on which I have run the queries . I am getting NEGATIVE, yes, NEGATIVE results. What does this mean ?

  I am getting values like

  -.047
  -18.99
  -2.31
  -.69 etc. 

   What does this mean ?

                                                Tapan Received on Thu Aug 05 1999 - 10:38:25 CDT