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oracle性能优化参数调整

原创 Linux操作系统 作者:pgstar 时间:2009-03-02 11:22:30 0 删除 编辑

1.SHARE_POOL_SIZE

数据字典的命中率计算:
select ((1 - (Sum(GetMisses) / (Sum(Gets) + Sum(GetMisses)))) * 100) "Hit Rate"
 from V$RowCache
where Gets + GetMisses <> 0;
数据字典的命中率低于95%可考虑提升SHARE_POOL_SIZE

LIBRARY CACHE(reload)的命中率计算:

select Sum(Pins) "Hits",Sum(Reloads) "Misses",((Sum(Reloads) / Sum(Pins)) * 100)"Reload %"
from V$LibraryCache;


LIBRARY CACHE的命中率计算:

select Sum(Pins) "Hits",Sum(Reloads) "Misses",Sum(Pins) / (Sum(Pins) + Sum(Reloads)) "Hit Ratio"
from V$LibraryCache;

LIBRARY CACHE(reload)的命中率高于1%或LIBRARY CACHE命中率低于95%可考虑增大SHARE_POOL_SIZE

2.db_cache_size

data cache hit ratio计算:

select sum(decode(name,'physical reads',value,0)) phys,
   sum(decode(name,'db block gets',value,0)) gets,sum(decode(name,'consistent gets', value,0)) con_gets,
   (1 - (sum(decode(name,'physical reads',value,0)) /
   (sum(decode(name,'db block gets',value,0)) +
   sum(decode(name,'consistent gets',value,0))))) * 100 hitratio
from v$sysstat;

一般可让命中率保持95%以上

可通过查看V$DB_CHCHE_ADVICE视图,确定要不要调整:

NAME       SIZE_FOR_ESTIMATE SIZE_FACTOR  ESTD_PHYSICAL_READ_FACTOR
--------------------    -----------------      -----------      -------------------------
DEFAULT         4        .1667 1        .8136
DEFAULT         8        .3333         1.0169
DEFAULT        12         .5          1.0085
DEFAULT        16         .6667           1
DEFAULT       20                                .8333            1
DEFAULT                            24                                   1                                                1

由上可看出ESTD_PHYSICAL_READ_FACTOR达到1时SIZE_FOR_ESTIMATE 为16,而当前的值为(SIZE_FACTOR)列24,因此可考虑适当减少DB_CACHE_SIZE.

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/216599/viewspace-558269/,如需转载,请注明出处,否则将追究法律责任。

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