select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
SESSIONS ACTIVE

alter database commit to switchover to primary;

重新启动数据库open

shutdown immediate

startup

select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
SESSIONS ACTIVE

select open_mode,database_role from v$database;

OPEN_MODE  DATABASE_ROLE
----------             ----------------
OPEN     PRIMARY

至此原主库切换至备库，原备库切换至主库了

3）应急切换

（注：模拟主库由于故障无法正常switchover，需要执行failover，强制备库->pridb并接管业务）

1.备库：

由于是failover，所以理解主库这时候已经无法正常使用，只需备库切换至pridb

停止应用恢复模式

alter database recover managed standby database finish;

转换standbydb为primary db

alter database commit to switchover to primary;

重启数据库，恢复正常业务

shutdown immediate

startup