standby flashback

admin

开启STANDBY库为READ WRITE
1.取消主库传送归档

1. SQL> alter system set log_archive_dest_state_2=defer;

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2.取消备库应用日志

1. SQL> alter database recover managed standby database cancel;

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3.修改相关参数

1. SQL> alter system db_recovery_file_dest='/oracle/fast_recovery_area';
   
2. SQL> alter system set db_recovery_file_dest_size=30G;
   
3. SQL> alter system set db_flashback_retention_target=1440;

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4.打开FLASHBACK

1. SQL> alter database flashback on;

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5.创建还原点

1. SQL> create restore point before_flashback guarantee flashback database;

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6.激活STANDBY DATABASE

1. SQL> alter database activate standby database;

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7.如果DG不是最大性能，则修改为最大性能

1. SQL> startup force mount;
   
2. SQL> alter database set standby database to maximize performance;
   
3. SQL> alter database open;

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8.查看数据库状态

1. SQL> select open_mode,database_role from v$database;

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此时，STANDBY库已经开启为READ WRITE
重新返回为STANDBY
1.将数据库启动至mount状态

1. SQL> startup force mount;

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2.闪回

1. SQL> flashback database to restore point before_flashback;

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3.将数据库修改为STANDBY

1. SQL> alter database convert to physical standby;

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4.打开数据库

1. SQL> startup force mount;

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5.删除还原点（删除还原点需要数据库在mount状态，不可以是OPEN READ ONLY状态），关闭FLASHBACK

1. SQL> drop restore point before_flashback;
   
2. SQL> alter database flashback off;

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6.打开数据库并应用日志

1. SQL> alter database open read only;
   
2. SQL> alter database recover managed standby database disconnect;

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7.主库开启日志传输

1. SQL> alter system set log_archive_dest_state_2=enable;

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8.主库切换归档，验证备库是否可以应用