Oracle DataGuard切換步驟

ADG或者DG的切換步驟：

1. 可以切換的情況，主庫查詢
SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;
SWITCHOVER_STATUS
--------------------
TO STANDBY


2.如果主庫是上面的狀態，將主庫切換至備用模式
SQL> alter database commit to switchover to physical standby with session shutdown;


3.關閉、裝載主資料庫
SQL> shutdown immediate;
SQL> startup mount;
或者
SQL> startup；


4.檢視備庫準備向主庫模式切換
SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;
SWITCHOVER_STATUS
————————
TO PRIMARY
1 row selected
注：如果是TO PRIMARY表示可以正常切換，不過還會遇到NOT ALLOWED和PENDING或者LATENT，實際操作下來如果備庫的switchover_status為not allowed或者to primary都可以正常切換


5.切換備庫至主庫模式
SQL> alter database commit to switchover to primary with session shutdown;


6.開啟新的主資料庫
SQL> ALTER DATABASE OPEN;


7. 在新的備庫伺服器上啟動 REDO apply。
SQL> alter database open; 
SQL> alter database recover managed standby database using current logfile disconnect from session;