（1）检查主数据库，是否支持转换
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO STANDBY
在switchover_stauts中如果不是to standy或者sessions active，则检查DG配置是否运行正常，如果
是session active，则需要确定并终止可能阻碍切换处理的活动或者sql会话，如果之后列还是显示
sessions active，可以通过添加with session shutdown来执行切换
（2）在主数据库上发起切换
SQL> alter database commit to switchover to physical standby;
Database altered.
警告日志文件如下
Stopping background process CJQ0
Wed Oct 16 17:03:17 2013
SMON: disabling tx recovery
Wed Oct 16 17:03:17 2013
Stopping background process QMNC
Waiting for dispatcher 'D000' to shutdown
All dispatchers and shared servers shutdown
Stopping background process FBDA
SMON: disabling cache recovery
Wed Oct 16 17:03:27 2013
Shutting down archive processes
Archiving is disabled
Wed Oct 16 17:03:27 2013
ARC1: Becoming the heartbeat ARCH
ARC1: Archiving disabled
ARCH shutting down
ARC1: Archival stopped
Wed Oct 16 17:03:27 2013
ARCH shutting down
ARC3: Archival stopped
Wed Oct 16 17:03:27 2013
ARCH shutting down
ARC2: Archival stopped
Wed Oct 16 17:03:28 2013
ARCH shutting down
ARC0: Archival stopped
Thread 1 closed at log sequence 686
Successful close of redo thread 1
Wed Oct 16 17:03:31 2013
idle dispatcher 'D000' terminated, pid = (16, 1)
ARCH: Noswitch archival of thread 1, sequence 686
ARCH: End-Of-Redo Branch archival of thread 1 sequence 686
ARCH: Archiving is disabled due to current logfile archival
Using STANDBY_ARCHIVE_DEST parameter default value as /u01/arch1/DGBJ
LOG_ARCHIVE_DEST_2 is a potential switchover target
Backup controlfile written to trace file
/u01/app/oracle/diag/rdbms/dgbj/DGBJ/trace/DGBJ_ora_28009.trc
Clearing standby activation ID 775996802 (0x2e40c582)
The primary database controlfile was created using the
'MAXLOGFILES 16' clause.
There is space for up to 13 standby redo logfiles
Use the following SQL commands on the standby database to create
standby redo logfiles that match the primary database:
ALTER DATABASE ADD STANDBY LOGFILE 'srl1.f' SIZE 52428800;
ALTER DATABASE ADD STANDBY LOGFILE 'srl2.f' SIZE 52428800;
ALTER DATABASE ADD STANDBY LOGFILE 'srl3.f' SIZE 52428800;
ALTER DATABASE ADD STANDBY LOGFILE 'srl4.f' SIZE 52428800;
Archivelog for thread 1 sequence 686 required for standby recovery
Wed Oct 16 17:03:40 2013
MRP0 started with pid=20, OS id=30611
MRP0: Background Managed Standby Recovery process started (DGBJ)
Fast Parallel Media Recovery NOT enabled
Managed Standby Recovery not using Real Time Apply
parallel recovery started with 2 processes
Online logfile pre-clearing operation disabled by switchover
Media Recovery Log /u01/arch1/DGBJ/log1_686_826058126.arc
Identified End-Of-Redo for thread 1 sequence 686
Resetting standby activation ID 775996802 (0x2e40c582)
Media Recovery End-Of-Redo indicator encountered
Media Recovery Applied until change 10410462
MRP0: Media Recovery Complete: End-Of-REDO (DGBJ)
MRP0: Background Media Recovery process shutdown (DGBJ)
Wed Oct 16 17:03:57 2013
Switchover: Complete - Database shutdown required (DGBJ)
Completed: alter database commit to switchover to physical standby
（3）重新启动主实例到mount
SQL> shutdown immediate;
ORA-01507: database not mounted
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 318046208 bytes
Fixed Size 1299652 bytes
Variable Size 289409852 bytes
Database Buffers 20971520 bytes
Redo Buffers 6365184 bytes
Database mounted.
SQL>
（4）在备用数据库检查是否支持转换到primary
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
返回值是to promary 或者 sessions active，这表示备用数据库已经准备好切换到主角色，
（5）转换物理standby 到primary
SQL> alter database commit to switchover to primary;
Database altered.
警告日志
Backup controlfile written to trace file
/u01/app/oracle/diag/rdbms/dgwh/DGWH/trace/DGWH_ora_712.trc
SwitchOver after complete recovery through change 10410462
Online log /u01/app/oracle/oradata/DGWH/onlinelog/o1_mf_1_96bsf1w0_.log: Thread 1 Group 1
was previously cleared
Online log /u01/app/oracle/flash_recovery_area/DGWH/onlinelog/o1_mf_1_96bsftsy_.log: Thread
1 Group 1 was previously cleared
Online log /u01/app/oracle/oradata/DGWH/onlinelog/o1_mf_2_96bj1jvq_.log: Thread 1 Group 2
was previously cleared
Online log /u01/app/oracle/flash_recovery_area/DGWH/onlinelog/o1_mf_2_96bj25wh_.log: Thread
1 Group 2 was previously cleared
Online log /u01/app/oracle/oradata/DGWH/onlinelog/o1_mf_3_96bj387h_.log: Thread 1 Group 3
was previously cleared
Online log /u01/app/oracle/flash_recovery_area/DGWH/onlinelog/o1_mf_3_96bj4px8_.log: Thread
1 Group 3 was previously cleared
Standby became primary SCN: 10410460
Converting standby mount to primary mount.
Switchover: Complete - Database mounted as primary (DGWH)
Tue Oct 22 17:33:37 2013
ARC0: STARTING ARCH PROCESSES
Completed: alter database commit to switchover to primary
注意：转换前如果是最大可用或者最大保护模式，需要在standby上先创建standby redo log
alter database add standby logfile ('/u01/app/oracle/oradata/DGWH/onlinelog/standby01.log')
size 50m;
.....
另外需要检查参数standy log service属性是否正确
SQL> show parameter log_archive_dest_2;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
log_archive_dest_2 string SERVICE=DGBJ LGWR SYNC AFFIRM
VALID_FOR=(ONLINE_LOGFILES,PRI
MARY_ROLE) DB_UNIQUE_NAME=DGBJ
（5）打开新的primary数据库
需要先关闭，然后重启
SQL> shutdown immediate;
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 318046208 bytes
Fixed Size 1299652 bytes
Variable Size 301992764 bytes
Database Buffers 8388608 bytes
Redo Buffers 6365184 bytes
Database mounted.
（6）转换后的检查
-- 主库和备库角色
SQL> select database_role,protection_mode from v$database;
DATABASE_ROLE PROTECTION_MODE
---------------- --------------------
PRIMARY MAXIMUM AVAILABILITY
SQL> select database_role,protection_mode from v$database;
DATABASE_ROLE PROTECTION_MODE
---------------- --------------------
PHYSICAL STANDBY MAXIMUM AVAILABILITY
-- 日志序列是否同步
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /u01/arch1/DGWH
Oldest online log sequence 687
Next log sequence to archive 688
Current log sequence 688
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /u01/arch1/DGBJ
Oldest online log sequence 685
Next log sequence to archive 0
Current log sequence 688
--在转换后的备库启用redo apply
SQL> alter database open;
Database altered.
SQL> alter database recover managed standby database using current logfile disconnect from
session;
Database altered.
-- 在主库创建表test，检查是否正常同步
SQL> create table test as select rownum id from dual connect by rownum < 5;
Table created.
SQL> alter system switch logfile;
System altered.
备库：
select * from test
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL> /
select * from test
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL> /
ID
----------
1
2
3
4
