除了达到指定的文件大小并执行" ALTER SYSTEM SWITCH LOGFILE"以外，Oracle中过早重做日志切换的可能原因是什么？

在某些情况下，我们的某些(但不是全部)节点在填满之前过早地切换了重做日志文件。这种情况每5 15分钟发生一次，每种情况下日志的大小差异很大(从指定大小的15％到100％)。

解决方案

回答

本文说，它在RAC中的行为有所不同。

In a parallel server environment, the
  LGWR process in each instance holds a
  KK instance lock on its own thread.
  The id2 field identifies the thread
  number. This lock is used to trigger
  forced log switches from remote
  instances. A log switch is forced
  whenever the current SCN for a thread
  falls behind the force SCN recorded in
  the database entry section of the
  controlfile. The force SCN is one more
  than the highest high SCN of any log
  file reused in any thread.