1、select physical_reads/(db_block_gets+consistent_gets) from v$buffer_pool_statistics；

结果：
   0.377767192556395

2、SELECT a.VALUE + b.VALUE logical_reads,
c.VALUE phys_reads,
round(100*(1-c.value/(a.value+b.value)),4) hit_ratio
FROM v$sysstat a,v$sysstat b,v$sysstat c
WHERE a.NAME='db block gets'
AND b.NAME='consistent gets'
AND c.NAME='physical reads';

结果：    logical_reads       phys_reads          hit_ratio
562713821869 8280258719 98.5285

为什么两次执行的命中率差别这么大？

ITPub博客

命中率问题

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