六、DG_broker工具管理切换DG主备

6.1、设置primary和standby启动时参数文件为spfile

show parameter spfile;

6.2、给切换后的主备库都设置 DG_BROKER_START为TRUE

alter system set dg_broker_start=true scope=both;
!ps -ef|grep dmon
show parameter dg_broker_start;
SELECT d.DBID,
d.DB_UNIQUE_NAME,
d.FORCE_LOGGING,
d.FLASHBACK_ON,
d.FS_FAILOVER_STATUS,
d.FS_FAILOVER_CURRENT_TARGET,
d.FS_FAILOVER_THRESHOLD,
d.FS_FAILOVER_OBSERVER_PRESENT,
d.FS_FAILOVER_OBSERVER_HOST
FROM v$database d;

6.3、配置监听

需要在listener.ora静态添加一个service_name为db_unique_name_DGMGRL.db_domain的注册。这个service_name会在DGMGRL重启数据库的时候用到。 通过DGMGRL重启数据库时DMON进程会先将数据库关闭，然后DGMGRL用此service_name通过listener连接到数据库，发出启动命令。 tnsnames.ora主备库要保持一致。

切换后新主库(原备库)uni_dg2静态监听文件：

[oracle@dbstandby08 ~]$ cat /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1/network/admin/listener.ora
# listener.ora Network Configuration File: /u01/oracle/product/11.2.0/db/network/admin/listener

.ora
# Generated by Oracle configuration tools.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS_LIST = 
        (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.8)(PORT = 1521))
      )
    )
  )

SID_LIST_LISTENER = 
  (SID_LIST = 
    (SID_DESC = 
      (GLOBAL_DBNAME=orcl)
      (SID_NAME = orcl)
      (ORACLE_HOME = /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1)       
    ) 
    (SID_DESC =
      (GLOBAL_DBNAME = uni_dg2)
      (ORACLE_HOME = /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1)
      (SID_NAME = orcl)
    )
    (SID_DESC =
      (GLOBAL_DBNAME = uni_dg2_DGMGRL)
      (ORACLE_HOME = /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1)
      (SID_NAME = orcl)
    )
  ) 

ADR_BASE_LISTENER = /u01/oracle/tools/oracle11g

[oracle@dbstandby08 ~]$ cat /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1/network/admin/tnsnames.ora 
LISTENER_ORCL =
  (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.8)(PORT = 1521))

uni_dg1 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.7)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = orcl)
    )
  )

uni_dg2 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.8)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = orcl)
    )

  )

uni_dg1_DGMGRL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.7)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

uni_dg2_DGMGRL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.8)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )
  

切换后新备库（原主库）uni_dg1静态监听文件：

[oracle@dbprimary07 admin]$ cat /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1/network/admin/listener.ora
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = orcl)
      (ORACLE_HOME = /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1)
      (SID_NAME = orcl)
    )
    (SID_DESC =
      (GLOBAL_DBNAME = uni_dg1)  
      (ORACLE_HOME = /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1)  
      (SID_NAME = orcl)  
    )
      (SID_DESC =
      (GLOBAL_DBNAME = uni_dg1_DGMGRL)
      (ORACLE_HOME = /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1)
      (SID_NAME = orcl)
    )
  )

LISTENER =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.7)(PORT = 1521))
  )

ADR_BASE_LISTENER = /u01/oracle/tools/oracle11g

[oracle@dbprimary07 admin]$ cat /u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1/network/admin/tnsnames.ora
# tnsnames.ora Network Configuration File: /u01/app/oracle/product/11.2.0/db/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.

LISTENER_ORCL =
  (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.7)(PORT = 1521))

uni_dg1 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.7)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

uni_dg2 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.8)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

uni_dg1_DGMGRL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.7)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

uni_dg2_DGMGRL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.0.8)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl)
    )
  )

6.4、dgmgrl中配置broker并启用

[oracle@dbstandby08 dbs]$ ==dgmgrl== DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information. DGMGRL> ==connect sys/oracle@uni_dg2_DGMGRL== Connected

==#查看配置：== DGMGRL> show configuration Error: ORA-16525: the Data Guard broker is not yet available

Configuration details cannot be determined by DGMGRL

#如果之前有配置，请先移除
DGMGRL> REMOVE CONFIGURATION;
--查看参数文件的状态
DGMGRL> SHOW CONFIGURATION;
#创建新的参数文件CONFIGURATION：
DGMGRL> create configuration 'dg_broker' as primary database is 'uni_dg2' connect identifier is uni_dg2;
--添加备库：
DGMGRL> add database 'uni_dg1' as connect identifier is uni_dg1 maintained as physical;
--启用参数文件：
DGMGRL> ENABLE CONFIGURATION;
--查看参数文件的状态
DGMGRL> SHOW CONFIGURATION;
--启用备库
DGMGRL> ENABLE DATABASE 'uni_dg1'

--查看数据库详情
DGMGRL> show database verbose uni_dg1;
DGMGRL> show database verbose uni_dg2;

具体执行过程：

DGMGRL> create configuration 'dg_broker' as primary database is 'uni_dg2' connect identifier is uni_dg2;
Configuration "dg_broker" created with primary database "uni_dg2"
DGMGRL> 
DGMGRL> 
DGMGRL> add database 'uni_dg1' as connect identifier is uni_dg1 maintained as physical;
Database "uni_dg1" added
DGMGRL> ENABLE CONFIGURATION;
Enabled.
DGMGRL> SHOW CONFIGURATION;

Configuration - dg_broker

  Protection Mode: MaxPerformance
  Databases:
    uni_dg2 - Primary database
    uni_dg1 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL> ENABLE DATABASE 'uni_dg1'
Enabled.
DGMGRL> show database verbose uni_dg1;

Database - uni_dg1

  Role:            PHYSICAL STANDBY
  Intended State:  APPLY-ON
  Transport Lag:   0 seconds
  Apply Lag:       0 seconds
  Real Time Query: ON
  Instance(s):
    orcl

  Properties:
    DGConnectIdentifier             = 'uni_dg1'
    ObserverConnectIdentifier       = ''
    LogXptMode                      = 'ASYNC'
    DelayMins                       = '0'
    Binding                         = 'OPTIONAL'
    MaxFailure                      = '0'
    MaxConnections                  = '1'
    ReopenSecs                      = '300'
    NetTimeout                      = '30'
    RedoCompression                 = 'DISABLE'
    LogShipping                     = 'ON'
    PreferredApplyInstance          = ''
    ApplyInstanceTimeout            = '0'
    ApplyParallel                   = 'AUTO'
    StandbyFileManagement           = 'AUTO'
    ArchiveLagTarget                = '0'
    LogArchiveMaxProcesses          = '4'
    LogArchiveMinSucceedDest        = '1'
    DbFileNameConvert               = '/u01/oracle/tools/oracle11g/oradata/orcl, /u01/oracle/tools/oracle11g/oradata/orcl'
    LogFileNameConvert              = '/u01/oracle/tools/oracle11g/oradata/orcl, /u01/oracle/tools/oracle11g/oradata/orcl'
    FastStartFailoverTarget         = ''
    StatusReport                    = '(monitor)'
    InconsistentProperties          = '(monitor)'
    InconsistentLogXptProps         = '(monitor)'
    SendQEntries                    = '(monitor)'
    LogXptStatus                    = '(monitor)'
    RecvQEntries                    = '(monitor)'
    HostName                        = 'dbprimary07'
    SidName                         = 'orcl'
    StaticConnectIdentifier         = '(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=dbprimary07)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=uni_dg1_DGMGRL)(INSTANCE_NAME=orcl)(SERVER=DEDICATED)))'
    StandbyArchiveLocation          = '/u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1/dbs/arch'
    AlternateLocation               = ''
    LogArchiveTrace                 = '0'
    LogArchiveFormat                = '%t_%s_%r.dbf'
    TopWaitEvents                   = '(monitor)'

Database Status:
SUCCESS

DGMGRL> 
DGMGRL> show database verbose uni_dg2;

Database - uni_dg2

  Role:            PRIMARY
  Intended State:  TRANSPORT-ON
  Instance(s):
    orcl

  Properties:
    DGConnectIdentifier             = 'uni_dg2'
    ObserverConnectIdentifier       = ''
    LogXptMode                      = 'ASYNC'
    DelayMins                       = '0'
    Binding                         = 'optional'
    MaxFailure                      = '0'
    MaxConnections                  = '1'
    ReopenSecs                      = '300'
    NetTimeout                      = '30'
    RedoCompression                 = 'DISABLE'
    LogShipping                     = 'ON'
    PreferredApplyInstance          = ''
    ApplyInstanceTimeout            = '0'
    ApplyParallel                   = 'AUTO'
    StandbyFileManagement           = 'AUTO'
    ArchiveLagTarget                = '0'
    LogArchiveMaxProcesses          = '4'
    LogArchiveMinSucceedDest        = '1'
    DbFileNameConvert               = '/u01/oracle/tools/oracle11g/oradata/orcl, /u01/oracle/tools/oracle11g/oradata/orcl'
    LogFileNameConvert              = '/u01/oracle/tools/oracle11g/oradata/orcl, /u01/oracle/tools/oracle11g/oradata/orcl'
    FastStartFailoverTarget         = ''
    StatusReport                    = '(monitor)'
    InconsistentProperties          = '(monitor)'
    InconsistentLogXptProps         = '(monitor)'
    SendQEntries                    = '(monitor)'
    LogXptStatus                    = '(monitor)'
    RecvQEntries                    = '(monitor)'
    HostName                        = 'dbstandby08'
    SidName                         = 'orcl'
    StaticConnectIdentifier         = '(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=dbstandby08)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=uni_dg2_DGMGRL)(INSTANCE_NAME=orcl)(SERVER=DEDICATED)))'
    StandbyArchiveLocation          = '/u01/oracle/tools/oracle11g/product/11.2.0/dbhome_1/dbs/arch'
    AlternateLocation               = ''
    LogArchiveTrace                 = '0'
    LogArchiveFormat                = '%t_%s_%r.dbf'
    TopWaitEvents                   = '(monitor)'

Database Status:
SUCCESS

DGMGRL> 

6.5、查看主备状态

DGMGRL> show configuration;

Configuration - dg_broker

  Protection Mode: MaxPerformance
  Databases:
    uni_dg2 - Primary database
    uni_dg1 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

6.6、测试切换

当前新主库uni_dg2 switchover 到uni_dg1,让新备库uni_dg1再变成主库

DGMGRL>  switchover to uni_dg1;
Performing switchover NOW, please wait...
New primary database "uni_dg1" is opening...
Operation requires shutdown of instance "orcl" on database "uni_dg2"
Shutting down instance "orcl"...
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "orcl" on database "uni_dg2"
Starting instance "orcl"...
ORACLE instance started.
Database mounted.
Database opened.
Switchover succeeded, new primary is "uni_dg1"
DGMGRL> 
###提示:==此次切换uni_dg2库 不需要手动重启 ==

操作过程中可能遇到的报错:

DGMGRL> create configuration 'dg_broker' as primary database is 'uni_dg2' connect identifier is uni_dg2;
Error: 
ORA-16525: the Data Guard broker is not yet available
ORA-06512: at "SYS.DBMS_DRS", line 157
ORA-06512: at line 1

**说明uni_dg2库没开启 Data Guard broker 参数，需要执行下面指令开启 **

SQL > alter system set dg_broker_start=true scope=both;

6.7、切换完成后重新确认主备状态

主备库服务器上都执行操作以下指令

dgmgrl sys/oracle@uni_dg1 "SHOW CONFIGURATION;"
dgmgrl sys/oracle@uni_dg2 "SHOW CONFIGURATION;"

select database_role,protection_mode,protection_level,open_mode from v$database;

下面时具体执行过程：

[oracle@dbstandby08 arch]$ dgmgrl sys/oracle@uni_dg1 "SHOW CONFIGURATION;"
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.

Configuration - dg_broker

  Protection Mode: MaxPerformance
  Databases:
    uni_dg1 - Primary database
    uni_dg2 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS


[oracle@dbstandby08 arch]$ dgmgrl sys/oracle@uni_dg2 "SHOW CONFIGURATION;"
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.

Configuration - dg_broker

  Protection Mode: MaxPerformance
  Databases:
    uni_dg1 - Primary database
    uni_dg2 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

[oracle@dbprimary07 admin]$ dgmgrl sys/oracle@uni_dg1 "SHOW CONFIGURATION;"
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.

Configuration - dg_broker

  Protection Mode: MaxPerformance
  Databases:
    uni_dg1 - Primary database
    uni_dg2 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

dbprimary07机器操作：

SQL> set line 300 pages 300
SQL> 
SQL> select database_role,protection_mode,protection_level,open_mode from v$database;

DATABASE_ROLE                                    PROTECTION_MODE                                              PROTECTION_LEVEL                                             OPEN_MODE
------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------
PRIMARY                                          MAXIMUM PERFORMANCE                                          MAXIMUM PERFORMANCE                                          READ WRITE

SQL> 

dbprimary08机器操作：

SQL> set line 300 pages 300;
SQL> select database_role,protection_mode,protection_level,open_mode from v$database;

DATABASE_ROLE                                    PROTECTION_MODE                                              PROTECTION_LEVEL                                             OPEN_MODE
------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------
PHYSICAL STANDBY                                 MAXIMUM PERFORMANCE                                          MAXIMUM PERFORMANCE                                          READ ONLY WITH APPLY

SQL> 

6.8 当前主库写入数据测试同步

当前主库dbprimary07写入数据

CREATE TABLE test (
    employee_id NUMBER PRIMARY KEY,
    first_name VARCHAR2(50),
    last_name VARCHAR2(50),
    hire_date DATE,
    salary NUMBER
);

INSERT INTO test(employee_id, first_name, last_name, hire_date, salary)
VALUES (1, 'John', 'Doe', '01-Jan-2021', 001);
commit;

操作过程：

SQL> CREATE TABLE test (
  2      employee_id NUMBER PRIMARY KEY,
  3      first_name VARCHAR2(50),
  4      last_name VARCHAR2(50),
  5      hire_date DATE,
  6      salary NUMBER
  7  );

INSERT INTO test(employee_id, first_name, last_name, hire_date, salary) VALUES (1, 'John', 'Doe', '01-Jan-2021', 001);

Table created.

SQL> SQL>   2  
1 row created.

SQL> commit;

Commit complete.

SQL> select * from test;

EMPLOYEE_ID FIRST_NAME
----------- ------------------------------------------------------------------------------------------------------------------------------------------------------
LAST_NAME                                                                                                                                              HIRE_DATE           SALARY
------------------------------------------------------------------------------------------------------------------------------------------------------ --------------- ----------
          1 John
Doe                       

当前备库库dbstandby08上确认数据已经同步完成：

SQL> select * from test;

EMPLOYEE_ID FIRST_NAME
----------- ------------------------------------------------------------------------------------------------------------------------------------------------------
LAST_NAME                                                                                                                                              HIRE_DATE              SALARY
------------------------------------------------------------------------------------------------------------------------------------------------------ ------------------ ----------
          1 John
Doe                                                                                                                                                    01-JAN-21                   1

SQL>

6.8、第二次手动切换到uni_dg2 让uni_dg2重新变为主库

切换前查看当前的库信息：

[oracle@dbprimary07 dbs]$ dgmgrl sys/oracle@uni_dg2 
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> 
DGMGRL> 
DGMGRL>  show configuration verbose;

Configuration - dg_broker

  Protection Mode: MaxPerformance
  Databases:
    uni_dg1 - Primary database
    uni_dg2 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

#switchover to uni_dg2;

下面是具体的执行过程:

DGMGRL> 
DGMGRL>  switchover to uni_dg2;
Performing switchover NOW, please wait...
New primary database "uni_dg2" is opening...
Operation requires shutdown of instance "orcl" on database "uni_dg1"
Shutting down instance "orcl"...
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "orcl" on database "uni_dg1"
Starting instance "orcl"...
Unable to connect to database
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

Failed.
Warning: You are no longer connected to ORACLE.

Please complete the following steps to finish switchover:
        start up instance "orcl" of database "uni_dg1"

查看数据库状态:

dgmgrl sys/oracle@uni_dg1 'show configuration;'
dgmgrl sys/oracle@uni_dg2 'show configuration;'

[oracle@dbprimary07 dbs]$ dgmgrl sys/oracle@uni_dg1 'show configuration;'
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
Error: 
ORA-01034: ORACLE not available
Process ID: 0
Session ID: 0 Serial number: 0

Configuration details cannot be determined by DGMGRL
[oracle@dbprimary07 dbs]$ 
[oracle@dbprimary07 dbs]$ 
[oracle@dbprimary07 dbs]$ 
[oracle@dbprimary07 dbs]$ dgmgrl sys/oracle@uni_dg2 'show configuration;'
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.

Configuration - dg_broker

  Protection Mode: MaxPerformance
  Databases:
    uni_dg2 - Primary database
      Error: ORA-16778: redo transport error for one or more databases

    uni_dg1 - Physical standby database
      Error: ORA-01034: ORACLE not available

Fast-Start Failover: DISABLED

Configuration Status:
ERROR


[oracle@dbprimary07 dbs]$ ps -ef|grep ora_
oracle    47068  41514  0 22:02 pts/5    00:00:00 grep --color=auto ora_

####提示uni_dg1 数据库不可用，需要手动重启原主库####

机器dbstandby08操作查看数据库状态：

dgmgrl sys/oracle@uni_dg2 "SHOW CONFIGURATION;"
dgmgrl sys/oracle@uni_dg1 "SHOW CONFIGURATION;"

select database_role,protection_mode,protection_level,open_mode from v$database;

下面是具体的执行过程：

[oracle@dbstandby08 arch]$ dgmgrl sys/oracle@uni_dg2 "SHOW CONFIGURATION;"
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.

Configuration - dg_broker

 Protection Mode: MaxPerformance
 Databases:
   uni_dg2 - Primary database
   uni_dg1 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

[oracle@dbstandby08 arch]$ 
[oracle@dbstandby08 arch]$ dgmgrl sys/oracle@uni_dg1 "SHOW CONFIGURATION;"
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.

Configuration - dg_broker

 Protection Mode: MaxPerformance
 Databases:
   uni_dg2 - Primary database
   uni_dg1 - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

SQL> set line 300 pages 300
SQL> 
SQL> select database_role,protection_mode,protection_level,open_mode from v$database;

DATABASE_ROLE                                    PROTECTION_MODE                                              PROTECTION_LEVEL                                             OPEN_MODE
------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------ ------------------------------------------------------------
PRIMARY                                          MAXIMUM PERFORMANCE                                          MAXIMUM PERFORMANCE                                          READ WRITE

SQL> 

再次切换到uni_dg1，让uni_dg1再次变为主库时,uni_dg2不需要手动进行重启

[oracle@dbstandby08 dbs]$ dgmgrl sys/oracle@uni_dg1 
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> 
DGMGRL>  switchover to uni_dg1;
Performing switchover NOW, please wait...
New primary database "uni_dg1" is opening...
Operation requires shutdown of instance "orcl" on database "uni_dg2"
Shutting down instance "orcl"...
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "orcl" on database "uni_dg2"
Starting instance "orcl"...
ORACLE instance started.
Database mounted.
Database opened.
Switchover succeeded, new primary is "uni_dg1"
DGMGRL> 

以上就是整个DG_broker工具管理切换DG主备切换的过程，可以看到切换过程还是非常丝滑的，应用和维护还是很方便的。