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null event不是空事件不是没有等待事件而是Oracle忘记了刚才等待的事件的名字是什么了但保留了该事件的真实情况Oracle 的开发人员直到才更新了这些事件名称 那是不是我们每当遇到性能问题的时候都要patch到呢？ 我们已经知道他的真实情况依然在v$session_wait的PPP参数里体现所以我们可以从这些参数顺籐摸瓜找出这个null event 到底是什么等待事件 下面是ITPUB上COPY过来的一些信息 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 目前已经被证实的会涉及到null event 的等待事件还有有SQL*Net message to client db file scattered (or sequential) read |
