如何實現Oracle Data Guard主庫備庫角色切換

如何實現Oracle Data Guard主庫備庫角色切換，很多新手對此不是很清楚，為了幫助大家解決這個難題，下面小編將為大家詳細講解，有這方面需求的人可以來學習下，希望你能有所收獲。

步驟1：驗證主庫能否進行角色切換，TO STANDBY表示可以進行

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS 

----------------- 

TO STANDBY 

1 row selected

The TO STANDBY value in the SWITCHOVER_STATUS column indicates that it is 

possible to switch the primary database to the standby role. If the TO STANDBY value

is not displayed, then verify the Data Guard configuration is functioning correctly (fo

example, verify all LOG_ARCHIVE_DEST_n parameter values are specified correctly).

If the value in the SWITCHOVER_STATUS column is SESSIONS ACTIVE, perform. the

steps described in SectionA.4, "Problems Switching Over to a Standby Database" on 

pageA-4 to identify and terminate active user or SQL sessions that might prevent a 

switchover from being processed. If, after performing these steps, the SWITCHOVER_

STATUS column still displays SESSIONS ACTIVE, you can successfully perform. a 

switchover by appending the WITH SESSION SHUTDOWN clause to the ALTER 

DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY statement 

described in Step 2.

See Oracle Database Reference for information about other valid values for the 

SWITCHOVER_STATUS column of the V$DATABASE view.

步驟2：在主庫上執行角色切換到從庫角色

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY;

After this statement completes, the primary database is converted into a standby 

database. The current control file is backed up to the current SQL session trace file 

before the switchover. This makes it possible to reconstruct a current control file, if 

necessary.

步驟3：關閉并重新啟動之前的主庫實例

SQL> SHUTDOWN IMMEDIATE;

SQL> STARTUP MOUNT;

At this point in the switchover process, both databases are configured as standby 

databases.

步驟4：在備庫的V$DATABASE視圖中查看備庫的切換狀態

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE; 

SWITCHOVER_STATUS 

----------------- 

TO_PRIMARY 

1 row selected

If the value in the SWITCHOVER_STATUS column is SESSIONS ACTIVE, perform. the 

steps described in SectionA.4, "Problems Switching Over to a Standby Database" on 

pageA-4 to identify and terminate active user or SQL sessions that might prevent a 

switchover from being processed. If, after performing these steps, the SWITCHOVER_

STATUS column still displays SESSIONS ACTIVE, you can proceed to Step 5, and 

append the WITH SESSION SHUTDOWN clause to the switchover statement. See Oracle 

Database Reference for information about other valid values for the SWITCHOVER_

STATUS column of the V$DATABASE view

步驟5：切換備庫到主庫角色

You can switch a physical standby database from the standby role to the primary role 

when the standby database instance is either mounted in Redo Apply mode or open 

for read-only access. It must be in one of these modes so that the primary database 

switchover request can be coordinated. After the standby database is in an appropriate 

mode, issue the following SQL statement on the physical standby database that you 

want to change to the primary role:

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;

步驟6：完成備庫到主庫的切換

1. 如果備庫沒有以只讀模式打開，直接執行以下語句打開到新的主庫。

SQL> ALTER DATABASE OPEN;

2. 如果備庫以只讀模式打開，先關閉數據，然后再重新啟動。

SQL> SHUTDOWN IMMEDIATE;

SQL> STARTUP;

步驟7：如果有必要，重新啟動一下新的備庫上的重做日志應用服務

For the new physical standby database and for each other physical or logical standby 

database in the Data Guard configuration, if log apply services were not previously 

configured to continue operating through a switchover, use an appropriate command 

to restart log apply services. See Chapter6, "Log Apply Services" for more information 

about how to configure and start log apply services.

SQL> alter database recover managed standby database disconnect from session;

（注：可以通過select message from v$dataguard_status;查看當前備庫應用重做日志的狀態）

步驟8：開始發送重做數據到備庫上

Issue the following statement on the new primary database: 

SQL> ALTER SYSTEM SWITCH LOGFILE;

v$database Switchover_Status值的含義

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