10g_dataguard_failover
大體步驟：
1、啟動failover
SQL> alter database recover managed standby database finish force;
FORCE 關鍵字將會停止當前活動的RFS 程式，以便立刻執行failover。
剩下的步驟就與前面switchover 很相似了
2、切換物理standby 角色為primary
SQL> alter database commit to switchover to primary;
3、啟動新的primary 資料庫。
SQL> alter database open;
這樣就可以了，不需要在主庫上做啥操作。
如果想再將已經切換的系統變回原形，那就需要重新配置dg，因為在failover之後，原來的主庫就不是dg的一部分了。如果重新配置dg，那就要以原來的備庫（現在的主庫）作為主庫了，因為他在後續有很多操作了已經（無論是測試還是真正的火災他必定是已經當了很久的主庫了），待重新配置完dg之後，再做一次switchover切換，就可以將dg完完全全的恢復到我們所有測試之前的角色模式了。
實驗：
環境：
主庫：150-----因為是failover，所以在切換角色時150不需要做任何操作
備庫：200
1、200上：
SQL> alter database recover managed standby database finish force;
SQL> alter database commit to switchover to primary;
SQL> alter database open;
SQL> select switchover_status from v$database;
2、此時檢視原來的主庫150的狀態
解析：如果想再將已經切換的系統變回原形，那就需要重新配置dg，因為在failover之後，原來的主庫就不是dg的一部分了。如果重新配置dg，那就要以原來的備庫（現在的主庫）作為主庫了，因為他在後續有很多操作了已經（無論是測試還是真正的火災他必定是已經當了很久的主庫了），待重新配置完dg之後，再做一次switchover切換，就可以將dg完完全全的恢復到我們所有測試之前的角色模式了
3、重新配置DG以便將所有角色切換到最開始的狀態（150主庫，200備庫）
3.1 引數檔案不需要改變
3.2 在200（此時主庫）建立備庫控制檔案並scp到150
[oracle@stream dbs]$ sqlplus / as sysdba
SQL> create spfile from pfile;
SQL> startup mount
SQL> alter database create standby controlfile as '/u01/control01.dbf';
SQL> exit
[oracle@stream dbs]$ cd /u01
[oracle@stream u01]$ scp control01.dbf 192.168.249.150:/u01/app/oracle/oradata/ora10g/
3.3 將200（此時主庫）的資料檔案和日誌檔案傳到150上
[oracle@stream u01]$ cd app/oracle/oradata/ora10g/
[oracle@stream ora10g]$ scp *.dbf *.log 192.168.249.150:/u01/app/oracle/oradata/ora10g/
3.4 在200上將主庫啟動到open狀態
[oracle@stream ora10g]$ sqlplus / as sysdba
SQL> alter database open;
SQL> select name,database_role,open_mode,protection_mode from v$database;
NAME DATABASE_ROLE OPEN_MODE PROTECTION_MODE
--------- ---------------- ---------- --------------------
ORA10G PRIMARY READ WRITE MAXIMUM PERFORMANCE
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS---狀態不正常應該是因為150（備庫）還沒有mount，也沒應用redo
--------------------
NOT ALLOWED
3.5 啟動此時的備庫150到mount
SQL> startup mount
ORACLE instance started.
Total System Global Area 373293056 bytes
Fixed Size 1273780 bytes
Variable Size 113246284 bytes
Database Buffers 255852544 bytes
Redo Buffers 2920448 bytes
Database mounted.
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /arch/log
Oldest online log sequence 1
Next log sequence to archive 2
Current log sequence 2
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /arch/log
Oldest online log sequence 1
Next log sequence to archive 2
Current log sequence 2
3.6 備庫應用redo
SQL> alter database recover managed standby database disconnect from session;
Database altered.
3.7 在200上切換日誌
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /arch/log
Oldest online log sequence 3
Next log sequence to archive 5
Current log sequence 5
SQL> alter system switch logfile;
System altered.
SQL> /
System altered.
SQL> /
System altered.
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS---
--------------------
TO STANDBY
SQL> !date
Fri May 11 00:41:35 CST 2012
3.8 備庫檢視歸檔是否已經傳遞過來
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /arch/log
Oldest online log sequence 1
Next log sequence to archive 2
Current log sequence 2
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /arch/log
Oldest online log sequence 1
Next log sequence to archive 2
Current log sequence 2
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /arch/log
Oldest online log sequence 1
Next log sequence to archive 0
Current log sequence 8
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
SESSIONS ACTIVE
待DG重新搭建好以後（200為主庫，150為備庫），現在再將150變為主庫，200變為備庫
4、 切換
4.1 200上
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO STANDBY
SQL> !date
Fri May 11 00:41:35 CST 2012
SQL> alter database commit to switchover to physical standby;
Database altered.
SQL> shutdown immediate
ORA-01507: database not mounted
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 373293056 bytes
Fixed Size 1273780 bytes
Variable Size 113246284 bytes
Database Buffers 255852544 bytes
Redo Buffers 2920448 bytes
Database mounted.
SQL> alter database recover managed standby database disconnect from session;
Database altered.
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
SESSIONS ACTIVE
SQL> select name,database_role,open_mode,protection_mode from v$database;
NAME DATABASE_ROLE OPEN_MODE PROTECTION_MODE
--------- ---------------- ---------- --------------------
ORA10G PHYSICAL STANDBY MOUNTED MAXIMUM PERFORMANCE
4.2 150上：
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
SESSIONS ACTIVE
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
SQL> alter database commit to switchover to primary;
Database altered.
SQL> alter database open;
Database altered.
SQL> select name,database_role,open_mode,protection_mode from v$database;
NAME DATABASE_ROLE OPEN_MODE PROTECTION_MODE
--------- ---------------- ---------- --------------------
ORA10G PRIMARY READ WRITE MAXIMUM PERFORMANCE
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO STANDBY
5、此時已經完全恢復到我們所做測試前的狀態
測試完畢！！
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