Latch Free

 

1.cache buffer chains表明数据库存在单独的block竞争.如果有该事件，v$session_wait中P1对应latch地址，P2表示latch编号，P3表示为了获得该latch而尝试的次数。

 

select addr,latch#,gets,misses,sleeps
from v$latch_children
where sleeps > 0
and latch#=98
order by sleeps desc

 

2.查看sleep较多的子latch对应哪些对象

select distinct a.owner,a.segment_name,a.segment_type from
dba_extents a,
(select dbarfil, dbablk from x$bh where hladdr in
(select addr from (select addr from v$latch_children order by sleeps desc) where rownum <5 )
)b
where a.relative_fno=b.dbarfil
and a.block_id <=b.dbablk and a.block_id + a.blocks > b.dbablk;

 

3.在对应的SQL查询了这些对象

 

reference