DataGuard主备切换

1、SwitchOver

主库：

ALTER DATABASE COMMIT TO SWITCHOVER TO physical STANDBY WITH SESSION SHUTDOWN;

备库：

ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN;
ALTER DATABASE OPEN;

2、FailOver

备库：

alter database  recover managed  standby  database cancel ;
alter database recover managed standby database finish force;
alter database  activate physical  standby  database;
alter database  open;

3、三种模式切换

主备库都要执行

（1）转换为最高可用，log_archive_dest_2需要配置LGWR SYNC AFFIRM

alter database set standby database to maximize availability;

（2）转换为最大性能，log_archive_dest_2需要配置LGWR ASYNC

alter database set standby database to maximize performance;

（3）转换为最大保护，log_archive_dest_2需要配置LGWR SYNC AFFIRM

alter database set standby database to maximize protection;