Normally, a switch occurs when the current online redo log file is full and writing must continue.
一般来说，当当前的在线重做日志文件已经满了并且还必须继续写的是偶，日志切换就会发生。
Redo records can also be written to a redo log file before the corresponding transaction is committed.
基本意思如下对于重做记录，在相应的事务被提交之前，也能被写入重做日志文件。
You can add or drop online redo log file groups or members to the primary database without affecting the standby database.
你可以在主库添加或删除在线重做日志组或者日志成员而不影响备库。
Whenever you add an online redo log file to the primary database, you should add corresponding online and standby redo log files to the standby database.
无论何时，你在主库添加在线重做日志文件，你应该在备库添加相应的在线重做日志和备用重做日志文件。
If the redo log buffer fills, or another transaction commits, LGWR flushes all of the redo log entries in the redo log buffer to a redo log file, even though some redo records may not be committed.
例如如果重做日志缓冲满了，或者有其它的事务提交了。LGWR进程会把所有在重做日志缓冲中的重做日志事项写入重做文件，即使是一些重做记录可能还没有提交。
When the CPU load goes up, the time taken for a log file sync round trip can increase even when the number of log file syncs and the volume of redo log generated doesn't change.
CPU负荷增长尽管(写)事务量没有变写日志个数没有变日志文件同步的往返信号传输时间就会延长。
Now that you are confirmed that the lost redo file is an ACTIVE redo log, shutdown the database - shutdown immediate.
既然您确认丢失的重做文件是active重做日志，那么现在就可以关闭数据库——shutdownimmediate。
Now that you are confirmed that the lost redo file is an INACTIVE redo log, shutdown the database - shutdown immediate.
既然您已经确认丢失的重做文件是inactive重做日志，那么现在可以关闭数据库——shutdown immediate。
Now that you are confirmed that the lost redo file is an INACTIVE redo log, shutdown the database - shutdown immediate.
既然您已经确认丢失的重做文件是inactive重做日志，那么现在可以关闭数据库——shutdown immediate。
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