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9i中一個特殊等待事件--null event

2013-11-13 15:57:04  來源: Oracle 

  null event不是空事件不是沒有等待事件而是Oracle忘記了剛才等待的事件的名字是什麼了但保留了該事件的真實情況Oracle 的開發人員直到才更新了這些事件名稱
  
  那是不是我們每當遇到性能問題的時候都要patch到呢?
  
  我們已經知道他的真實情況依然在v$session_wait的PPP參數裡體現所以我們可以從這些參數順籐摸瓜找出這個null event 到底是什麼等待事件
  
  下面是ITPUB上COPY過來的一些信息
  
   LCK processes to pick up extra or missed posts (messages)
  In all cases that can be identified the wait time is zero
  although on most ports this is changed to /th second in
  order to force the process to be rescheduled
  
   Multiple DB writers
  
  Two cases:
  
   When the master has sent i/o requests to the slaves it
  waits on this event for up to seconds until the slaves
  signal that the i/o is complete
  
   The slaves wait on this event for up to seconds whilst
  waiting for requests from the master db writer
  
  目前已經被證實的會涉及到null event 的等待事件還有有SQL*Net message to client db file scattered (or sequential) read
From:http://tw.wingwit.com/Article/program/Oracle/201311/17565.html
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