Oracle數據庫主備切換

主備庫切換原因：

1. switch：用戶主動切換；

2. failover：主庫出現故障，強行切換；

 

switch切換過程：先主庫再備庫

 

主庫

1. 查看switchover_status：select database_role, switchover_status from v$database;

如果switchover_status為：to standby 則：

ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY

否則用：ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN;

 

2. 重啟數據庫：

shutdown immediate;

startup nomount;

 

3. 以備庫mount

alter database mount standby database;

 

備庫

1. 應用redo：alter database recover managed standby database disconnect from session;

 

2. 查看switchover_status：select database_role, switchover_status from v$database;

如果switchover_status為：to primary 則：ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY

否則用：ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN;

 

3.  重啟數據庫

shutdown immediate;

startup;

 

failover 主備庫切換

1.. 停止日志應用 
alter database recover managed standby database cancel; 

2. 關閉standby日志傳輸 
alter database recover managed standby database finish force;  

3. 切換到primary 
alter database commit to switchover to primary with session shutdown; 

做這一步的時候，若存在gap，則會報ORA-16139:Switchover: Media recovery required - standby not in limbo 錯誤。

做測試的時候，若先起主庫再起備庫，且未等待備庫相關日志傳輸完畢，就會出現這個問題。此時需要強制切換 
alter database activate physical standby database; 

 

4. 重啟數據庫到open狀態