判断Latch是否存在竞争

摘自【深入解析Oracle----作者：盖国强】

 

判断Latch是否存在竞争
如果MISSES对GETS比率超过1%，或者IMMEDIATE_MISSES对比(IMMEDIATE_GETS + IMMEDIATE_MISSES)比率超过1%，那么通常认为存在Latch竞争.

 

select substr(ln.name,1,20),gets,misses,immediate_gets,immediate_misses,immediate_misses/(immediate_gets+immediate_misses)*100 "百分比"
from v$latch l,v$latchname ln
where ln.NAME in ('redo allocation','redo copy') and ln.LATCH# = l.LATCH#;