【测试】DG的主切备，备切主

1.首先要应用日志，保持主备库一致：

备库：SBDB@SYS> recover managed standby database using current logfile disconnect from session;

Media recovery complete.

2.查看主备状态：

（1）主库：

ORA11GR2@SYS> select open_mode,protection_mode,database_role,switchover_status from v$database;

OPEN_MODE            PROTECTION_MODE      DATABASE_ROLE    SWITCHOVER_STATUS

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

READ WRITE           MAXIMUM PERFORMANCE  PRIMARY          SESSIONS ACTIVE

（2）备库：

SBDB@SYS>  select open_mode,protection_mode,database_role,switchover_status from v$database;

OPEN_MODE            PROTECTION_MODE      DATABASE_ROLE    SWITCHOVER_STATUS

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

READ ONLY            MAXIMUM PERFORMANCE  PHYSICAL STANDBY NOT ALLOWED

3.把主库切换为备库，重启后检查SWITCHOVER_STATUS为RECOVERY NEEDED:

ORA11GR2@SYS> alter database commit to switchover to physical standby with session shutdown;

Database altered.

ORA11GR2@SYS> shutdown abort

ORACLE instance shut down.

ORA11GR2@SYS>  startup mount

ORACLE instance started.

Total System Global Area  830930944 bytes

Fixed Size                  2257800 bytes

Variable Size             570428536 bytes

Database Buffers          255852544 bytes

Redo Buffers                2392064 bytes

Database mounted.

ORA11GR2@SYS> select switchover_status from v$database;

SWITCHOVER_STATUS

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

RECOVERY NEEDED

4.转换完备库恢复日志后，SWITCHOVER_STATUS为TO PRIMARY：

ORA11GR2@SYS>  recover managed standby database using current logfile disconnect from session;

Media recovery complete.

ORA11GR2@SYS>  select switchover_status from v$database;

SWITCHOVER_STATUS

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

TO PRIMARY

5.查看备库的状态，并应用日志，只有当SWITCHOVER_STATUS是sessions active或者是to_primary状态时才可以切换角色：

SBDB@SYS> recover managed standby database using current logfile disconnect from session;

Media recovery complete.

SBDB@SYS>  select switchover_status from v$database;

SWITCHOVER_STATUS

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

SESSIONS ACTIVE

6.切换备库并查看database_role，正常为primary：

SBDB@SYS>  alter database commit to switchover to primary with session shutdown;

Database altered.

SBDB@SYS>  alter database open;

Database altered.

SBDB@SYS>  select database_role from v$database;

DATABASE_ROLE

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

PRIMARY

SBDB@SYS> select switchover_status from v$database;

SWITCHOVER_STATUS

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

RESOLVABLE GAP

7.转换后在备库（切换之前的主库）应用日志，并查看状态：

ORA11GR2@SYS>  recover managed standby database using current logfile disconnect from session;

ORA-01153: an incompatible media recovery is active

ORA11GR2@SYS> recover managed standby database cancel;

Media recovery complete.

ORA11GR2@SYS> select switchover_status from v$database;

SWITCHOVER_STATUS

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

NOT ALLOWED

ORA11GR2@SYS> select database_role from v$database;

DATABASE_ROLE

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

PHYSICAL STANDBY

8.再次查看转换后主库（切换之前的备库）的switchover_status，正常应为TO STANDBY：

SBDB@SYS> select switchover_status from v$database;

SWITCHOVER_STATUS

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

TO STANDBY