db_cache_buffer修改策略

1.优化缓冲区大小、提高服务器的命中率
db_cache_size big integer 838860800
2.查看缓冲区命中率是否需要调优.

select 1 - ((physical.value - direct.value - lobs.value) / logical.value)
"Buffer Cache Hit Ratio"
from v$sysstat physical,v$sysstat direct,v$sysstat lobs,v$sysstat logical
where physical.name = 'physical reads'
and direct.name='physical reads direct'
and lobs.name='physical reads direct (lob)'
and logical.name='session logical reads';
当命中率>90%说明命中率很高了

3。获取推荐的值
select name,size_for_estimate,v$db_cache_advice.ESTD_PHYSICAL_READS from v$db_cache_advice
where block_size='8192' and advice_status='ON';

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原文链接：https://blog.csdn.net/db5201/article/details/84215563