主备库角色转换

7.2.1 Switchovers Involving a Physical Standby Database

Step 1   Verify it is possible to perform a switchover.

1. 先查看转换状态

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS

 -----------------

 TO STANDBY                                ——可以装换为备库，也就是说是主库状态

如果 SWITCHOVER_STATUS是SESSIONS ACTIVE，则要在

ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY

后面加上WITH SESSION SHUTDOWN。

Step 2   Initiate the switchover on the primary database.

2. 将目前的主库变为物理备库

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY;

Step 3   Shut down and restart the former primary instance.

3. 重启之前的主库到mount状态

SQL> SHUTDOWN IMMEDIATE;

SQL> STARTUP MOUNT;

注：在这个时候，两个数据库都处于备库状态。

Step 4   Verify the switchover status in the V$DATABASE view.

查证备库的转换状态

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS

-----------------

TO_PRIMARY                                                     ——可以转换为主库，说明是备库状态

1 row selected

Step 5   Switch the target physical standby database role to the primary role.

将目标物理备库转换为主库

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY （WITH SESSION SHUTDOWN）;

Step 6   Finish the transition of the standby database to the primary role.

完成转换备库到主库

如果物理备库在最近一次启动时不是处于只读模式 opened in read-only mode，直接将数据库打开，然后下一步。

SQL> ALTER DATABASE OPEN;

 如果物理备库在最近一次启动时是只读模式，则先将数据库正常关闭再起库。

SQL> SHUTDOWN IMMEDIATE;

SQL> STARTUP;

Step 7   If necessary, restart log apply services on the standby databases.

如果有需要，在新备库上重新开启日志应用

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

Step 8   Begin sending redo data to the standby databases.

开始传输数据给备库

SQL> ALTER SYSTEM SWITCH LOGFILE;

7.2.1 Switchovers Involving a Physical Standby Database

Step 1   Verify it is possible to perform a switchover.

1. 先查看转换状态

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS

 -----------------

 TO STANDBY                                ——可以装换为备库，也就是说是主库状态

如果 SWITCHOVER_STATUS是SESSIONS ACTIVE，则要在

ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY

后面加上WITH SESSION SHUTDOWN。

Step 2   Initiate the switchover on the primary database.

2. 将目前的主库变为物理备库

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY;

Step 3   Shut down and restart the former primary instance.

3. 重启之前的主库到mount状态

SQL> SHUTDOWN IMMEDIATE;

SQL> STARTUP MOUNT;

注：在这个时候，两个数据库都处于备库状态。

Step 4   Verify the switchover status in the V$DATABASE view.

查证备库的转换状态

SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS

-----------------

TO_PRIMARY                                                     ——可以转换为主库，说明是备库状态

1 row selected

Step 5   Switch the target physical standby database role to the primary role.

将目标物理备库转换为主库

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY （WITH SESSION SHUTDOWN）;

Step 6   Finish the transition of the standby database to the primary role.

完成转换备库到主库

如果物理备库在最近一次启动时不是处于只读模式 opened in read-only mode，直接将数据库打开，然后下一步。

SQL> ALTER DATABASE OPEN;

 如果物理备库在最近一次启动时是只读模式，则先将数据库正常关闭再起库。

SQL> SHUTDOWN IMMEDIATE;

SQL> STARTUP;

Step 7   If necessary, restart log apply services on the standby databases.

如果有需要，在新备库上重新开启日志应用

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

Step 8   Begin sending redo data to the standby databases.

开始传输数据给备库

SQL> ALTER SYSTEM SWITCH LOGFILE;