ALTER DATABASE add standby LOGFILE GROUP 7 size 500M;
ALTER DATABASE add standby LOGFILE GROUP 8 size 500M;
ALTER DATABASE add standby LOGFILE GROUP 9 size 500M;
启用命令：
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE;
?
具体内容参见：
如何确保dg 已经正常，后台日志类似如下：
Mon Dec 22 10:03:04 CST 2014
RFS[1]: Archived Log: '+DATA/lixora/archivelog/1_23094_790186477.dbf'
Mon Dec 22 10:03:25 CST 2014
Media Recovery Log +DATA/lixora/archivelog/1_23094_790186477.dbf
Media Recovery Waiting for thread 1 sequence 23095 (in transit)
Mon Dec 22 10:05:53 CST 2014
RFS[2]: Archived Log: '+DATA/lixora/archivelog/1_23095_790186477.dbf'
Primary database is in MAXIMUM PERFORMANCE mode
RFS[2]: No standby redo logfiles of size 1024000 blocks exist
Mon Dec 22 10:05:55 CST 2014
Media Recovery Log +DATA/zhglptdg/archivelog/1_23095_790186477.dbf
Media Recovery Waiting for thread 1 sequence 23096 (in transit)
Mon Dec 22 10:05:57 CST 2014
RFS[2]: Archived Log: '+DATA/lixora/archivelog/1_23096_790186477.dbf'
Primary database is in MAXIMUM PERFORMANCE mode
RFS[2]: No standby redo logfiles of size 1024000 blocks exist
Mon Dec 22 10:06:00 CST 2014
Media Recovery Log +DATA/lixora/archivelog/1_23096_790186477.dbf
Media Recovery Waiting for thread 1 sequence 23097 (in transit)
类似一下日志，表明日志只是传过来，但是没有应用：
Tue Dec 16 17:28:48 CST 2014
Primary database is in MAXIMUM PERFORMANCE mode
RFS[3]: Successfully opened standby log 7: '+DATA/lixora/onlinelog/group_7.360.857131345'
Tue Dec 16 18:57:12 CST 2014
Primary database is in MAXIMUM PERFORMANCE mode
RFS[3]: Successfully opened standby log 8: '+DATA/lixora/onlinelog/group_8.361.857131375'
Tue Dec 16 20:12:13 CST 2014
Primary database is in MAXIMUM PERFORMANCE mode
RFS[3]: Successfully opened standby log 7: '+DATA/lixora/onlinelog/group_7.360.857131345'
Tue Dec 16 21:40:39 CST 2014
Primary database is in MAXIMUM PERFORMANCE mode
RFS[3]: Successfully opened standby log 8: '+DATA/lixora/onlinelog/group_8.361.857131375'
如何可以确保dg 正常：
1）v$archive_log.applied? 是否为yes
2）主库切换日志：ALTER system swtich logfile；
看备库v$database.CURRENT_SCN 是否有增长？
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