Oracle 等待事件
将自己遇到的Oracle 等待事件记录下来，待以后可以查录：
rdbms ipc message等待事件
The background processes (LGWR, DBWR, LMS0) use this event to indicate that they are idle and are waiting for the foreground processes to send them an IPC message to do some work.
Wait Time: Up to 3 seconds. The parameter timeout shows the true sleep time.
Parameter: timeout
The amount of time that the session waits for an IPC message
注：granule [?gr?nju:l] 区组，小颗粒
