Calculating Buffer Cache Hit Ratio
In oder to determin weather the SGA ist apropriately sized, the most importent piece of informaiton is the Buffer Cache Hit Ratio.
set pages 100 lin 120
col RATIO format 999.99 heading "BufferCache Hit Ratio"
SELECT
round(
100 *
(P1.value + P2.value - P3.value) /
(P1.value + P2.value),2) ||
'%' as RATIO
FROM v$sysstat P1, v$sysstat P2, v$sysstat P3
WHERE P1.name = 'db block gets'
AND P2.name = 'consistent gets'
AND P3.name = 'physical reads';
Previous:
Map corrupted block to segment
