DataGuard开启failover

1、修改保护模式

DGMGRL> edit configuration set protection mode as maxAvailability;
Succeeded.

2、修改日志同步方式

DGMGRL> show database verbose xiaohe 'LogXptMode'
  LogXptMode = 'ASYNC'
DGMGRL> show database verbose xiaohedg 'LogXptMode'
  LogXptMode = 'ASYNC'
DGMGRL> edit database xiaohe set property LogXptMode = 'SYNC';
Property "logxptmode" updated
DGMGRL> edit database xiaohedg set property LogXptMode = 'SYNC';
Property "logxptmode" updated
DGMGRL> 
DGMGRL> show database verbose xiaohe 'LogXptMode'
  LogXptMode = 'SYNC'
DGMGRL> show database verbose xiaohedg 'LogXptMode'
  LogXptMode = 'SYNC'

3、在dgmgrl中配置主库与standby数据库的FastStartFailoverTarget属性

DGMGRL> show database verbose xiaohe 'FastStartFailoverTarget';
  FastStartFailoverTarget = 'xiaohedg'
DGMGRL> show database verbose xiaohedg 'FastStartFailoverTarget';
  FastStartFailoverTarget = 'xiaohe'

这里已经不用配置了， 如果需要配置， 使用如下的命令：

edit database xiaohedg set property FastStartFailoverTarget='xiaohe';

4、启动observer

DGMGRL> start observer

Observer started

5、在另外一个终端查看failover状态

可以看到Observer: xiaohe_dg1， 这里监控的就是主库。

DGMGRL> show fast_start failover
Fast-Start Failover: DISABLED
  Threshold:        30 seconds
  Target:           (none)
  Observer:         xiaohe_dg1
  Lag Limit:        30 seconds
  Shutdown Primary: TRUE
  Auto-reinstate:   TRUE
Configurable Failover Conditions
  Health Conditions:
    Corrupted Controlfile          YES
    Corrupted Dictionary           YES
    Inaccessible Logfile            NO
    Stuck Archiver                  NO
    Datafile Offline               YES
  Oracle Error Conditions:
    (none)

6、激活failover功能

DGMGRL> enable fast_start failover;
Enabled.

7、模拟故障

（1）、将主库给shutdown abort

SQL> shutdown abort;
ORACLE instance shut down.

（2）、等一两分钟， 查看observer的日志

DGMGRL> start observer
Observer started
23:56:08.19  Saturday, March 18, 2017
Initiating Fast-Start Failover to database "xiaohe"...
Performing failover NOW, please wait...
Failover succeeded, new primary is "xiaohe"
23:56:11.64  Saturday, March 18, 2017

（3）、查看备库是否已经切换为主库

SQL> select open_mode from v$database;
OPEN_MODE
--------------------
READ WRITE

（4）、将故障的库重新启动

启动数据库报错：

SQL> startup
ORACLE instance started.
Total System Global Area  839282688 bytes
Fixed Size		    2233000 bytes
Variable Size		  494931288 bytes
Database Buffers	  339738624 bytes
Redo Buffers		    2379776 bytes
Database mounted.
ORA-16649: possible failover to another database prevents this database from
being opened

查看日志，下面的红色部分是新产生的日志：

DGMGRL> start observer
Observer started
23:56:08.19  Saturday, March 18, 2017
Initiating Fast-Start Failover to database "xiaohe"...
Performing failover NOW, please wait...
Failover succeeded, new primary is "xiaohe"
23:56:11.64  Saturday, March 18, 2017
00:05:46.24  Sunday, March 19, 2017
Initiating reinstatement for database "xiaohedg"...
Reinstating database "xiaohedg", please wait...
Operation requires shutdown of instance "xiaohedg" on database "xiaohedg"
Shutting down instance "xiaohedg"...
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "xiaohedg" on database "xiaohedg"
Starting instance "xiaohedg"...
ORACLE instance started.
Database mounted.
Continuing to reinstate database "xiaohedg" ...
Reinstatement of database "xiaohedg" succeeded
00:06:42.78  Sunday, March 19, 2017

等了几分钟后， 数据库自动恢复正常了。

经测试， 但故障的库只需要启动到mount状态， failover就能自动将库打开。