1>驗證主庫能夠切換到備用角色。
SELECT SWITCHOVER_STATUS FROM V$DATABASE;
SWITCHOVER_STATUS
--------------------
TO STANDBY
2>在主庫上面開始切換
alter database commit to switchover to physical standby with session shutdown ;
備庫的alertlog中會收到一條
Identified End-Of-Redo (switchover) for thread 1 sequence 30 at SCN 0x0.126064類似的消息，
說明主庫開始做角色轉換，並且沒有丟失數據。
startup mount ;
3> 驗證轉換目標已經準備好轉換爲主庫角色
SELECT SWITCHOVER_STATUS FROM V$DATABASE;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
這裏查詢出來的值不爲TO_PRIMARY即有點問題。
4> 轉換目標邏輯備用庫角色爲主庫角色。
sql> alter database commit to switchover to primary with session shutdown;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
Database altered.
打開新的主庫
sql> ALTER DATABASE OPEN;