Oracle Datagurad Failover
生产环境中，可能会有各种各样的原因导致数据库不能提供服务，例如数据库库的硬件故障，操作系统故障或软件bug，人为的失误(例如rm -rf /)等，在这种情况下，dataguard显得尤为重要，当主库不可用的时候，可以将备库failover成主库继续提供服务，failover和switchover不同的是，执行failover后，原有的dataguard配置将会失效且有可能会丢失部分数据，所以在生产环境中能用switchover解决的问题则应尽量采用switchover！一：使用sql命令执行failover
1：查看当前的主库是dg1，物理备库为dg2，将主库关闭，模拟主库故障
[*] $ dgmgrl /
[*] DGMGRL for Linux: Version 11.2.0.3.0 - 64bit Production
[*] Copyright (c) 2000, 2009, Oracle. All rights reserved.
[*] Welcome to DGMGRL, type "help" for information.
[*] Connected.
[*] DGMGRL> show configuration;
[*] Configuration - DG_BROKER_CONFIG
[*] Protection Mode: MaxAvailability
[*] Databases:
[*] dg1 - Primary database
[*] dg2 - Physical standby database
[*] Fast-Start Failover: DISABLED
[*] Configuration Status:
[*] SUCCESS
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ WRITE PRIMARY dg1 NO
[*] SQL> shutdown abort
[*] ORACLE instance shut down.
2：在备库dg2上执行failover过程，failover执行的命令和switchover类似，只是在这个过程中，主库已经不可用
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ ONLY WITH APPLY PHYSICAL STANDBY dg2 NO
[*] SQL> alter database recover managed standby database cancel;
[*] Database altered.
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ ONLY PHYSICAL STANDBY dg2 NO
[*] 出现这个错误说明日志并未完全的应用
[*] SQL> alter database commit to switchover to primary;
[*] alter database commit to switchover to primary
[*] *
[*] ERROR at line 1:
[*] ORA-16139: media recovery required
[*] SQL> alter database recover managed standby database using current logfile disconnect from session;
[*] Database altered.
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ ONLY WITH APPLY PHYSICAL STANDBY dg2 NO
[*] SQL> alter database recover managed standby database finish;
[*] Database altered.
[*] SQL> alter database commit to switchover to primary;
[*] Database altered.
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] MOUNTED PRIMARY dg2 NO
[*] SQL> alter database open;
[*] Database altered.
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ WRITE PRIMARY dg2 NO
二：使用datagurad broker进行failover
1:开启主库和备库的闪回功能，主要用于主库恢复后的reinstate操作，当前主库为dg2,备库为dg1
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ WRITE PRIMARY dg2 YES
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ ONLY WITH APPLY PHYSICAL STANDBY dg1 YES
[*] $ dgmgrl sys/123456@dg1
[*] DGMGRL for Linux: Version 11.2.0.3.0 - 64bit Production
[*] Copyright (c) 2000, 2009, Oracle. All rights reserved.
[*] Welcome to DGMGRL, type "help" for information.
[*] Connected.
[*] DGMGRL> show configuration;
[*] Configuration - DG_BROKER_CONFIG
[*] Protection Mode: MaxAvailability
[*] Databases:
[*] dg2 - Primary database
[*] dg1 - Physical standby database
[*] Fast-Start Failover: DISABLED
[*] Configuration Status:
[*] SUCCESS
2:关闭主库dg2,模拟主库故障
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ WRITE PRIMARY dg2 YES
[*] SQL> shutdown abort
[*] ORACLE instance shut down.
[*] DGMGRL> show configuration;
[*] Configuration - DG_BROKER_CONFIG
[*] Protection Mode: MaxAvailability
[*] Databases:
[*] dg2 - Primary database
[*] dg1 - Physical standby database
[*] Fast-Start Failover: DISABLED
[*] Configuration Status:
[*] ORA-01034: ORACLE not available
[*] ORA-16625: cannot reach database "dg2"
[*] DGM-17017: unable to determine configuration status
3：执行failover
[*] DGMGRL> failover to dg1;
[*] Performing failover NOW, please wait...
[*] Failover succeeded, new primary is "dg1"
[*] DGMGRL> show configuration;
[*] Configuration - DG_BROKER_CONFIG
[*] Protection Mode: MaxAvailability
[*] Databases:
[*] dg1 - Primary database
[*] Warning: ORA-16629: database reports a different protection level from the protection mode
[*] dg2 - Physical standby database (disabled)
[*] ORA-16661: the standby database needs to be reinstated
[*] Fast-Start Failover: DISABLED
[*] Configuration Status:
[*] WARNING
4:重新启动原主库dg2
[*] SQL> startup
[*] ORACLE instance started.
[*] Total System Global Area417546240 bytes
[*] Fixed Size 2228944 bytes
[*] Variable Size 352324912 bytes
[*] Database Buffers 54525952 bytes
[*] Redo Buffers 8466432 bytes
[*] Database mounted.
[*] ORA-16649: possible failover to another database prevents this database from
[*] being opened
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] MOUNTED PRIMARY dg2 YES
5:执行reinstate操作
[*] DGMGRL> reinstate database dg2;
[*] Reinstating database "dg2", please wait...
[*] Operation requires shutdown of instance "dg" on database "dg2"
[*] Shutting down instance "dg"...
[*] ORA-01109: database not open
[*] Database dismounted.
[*] ORACLE instance shut down.
[*] Operation requires startup of instance "dg" on database "dg2"
[*] Starting instance "dg"...
[*] 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 and reissue the REINSTATE command:
[*] start up and mount instance "dg" of database "dg2"
[*] SQL> conn /as sysdba
[*] Connected to an idle instance.
[*] SQL> startup
[*] ORACLE instance started.
[*] Total System Global Area417546240 bytes
[*] Fixed Size 2228944 bytes
[*] Variable Size 352324912 bytes
[*] Database Buffers 54525952 bytes
[*] Redo Buffers 8466432 bytes
[*] Database mounted.
[*] Database opened.
[*] SQL> select open_mode,database_role,db_unique_name,flashback_on from v$database;
[*] OPEN_MODE DATABASE_ROLE DB_UNIQUE_NAME FLASHBACK_ON
[*] -------------------- ---------------- -------------------- ------------------
[*] READ ONLY PHYSICAL STANDBY dg2 YES
[*] DGMGRL> show configuration;
[*] Configuration - DG_BROKER_CONFIG
[*] Protection Mode: MaxAvailability
[*] Databases:
[*] dg1 - Primary database
[*] dg2 - Physical standby database (disabled)
[*] ORA-16661: the standby database needs to be reinstated
[*] Fast-Start Failover: DISABLED
[*] Configuration Status:
[*] SUCCESS
[*] DGMGRL> enable database dg2;
[*] Error: ORA-16661: the standby database needs to be reinstated
[*] Failed.
[*] DGMGRL> reinstate database dg2;
[*] Reinstating database "dg2", please wait...
[*] Reinstatement of database "dg2" succeeded
[*] DGMGRL> show configuration;
[*] Configuration - DG_BROKER_CONFIG
[*] Protection Mode: MaxAvailability
[*] Databases:
[*] dg1 - Primary database
[*] dg2 - Physical standby database
[*] Fast-Start Failover: DISABLED
[*] Configuration Status:
[*] SUCCESS
总结
1：非到万不得已的情况，不使用failover，优先考虑switchover
2：若执行failover，则考虑使用sql命令完成
3：执行failover后，应及时备份数据，并重构dg环境
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