[20160222]Oracle 11G Data Guard Failover

[20160222]Oracle 11G Data Guard Failover-flush redo.txt

--連結: http://blog.csdn.net/tianlesoftware/article/details/6256542

在Oracle 11g裡，Data Guard 切換多了一個新的功能：flush redo。

Flush 能把沒有傳送的redo 從主庫傳送到standby庫。 只要主庫能啟動到mount 狀態，那麼Flush 就可以把沒有傳送的歸檔和current
online redo 傳送到備庫。

Flush語法：

SQL> ALTER SYSTEM FLUSH REDO TO target_db_name;

這裡的target_db_name 是我們在主庫的db_unique_name 名稱。 也就是在tnsnames.ora 檔案配置的。 Flush 會將未傳送的redo 從主庫
傳到備庫，並且等待redo 在standby 庫上apply 之後返回成功。 所以只要Flush成功，那麼Failover 就沒有主句丟失。

--自己測試看看：

1.主庫：
SYS@test> show parameter unique
NAME            TYPE    VALUE
--------------- ------- -------
db_unique_name  string  test

--關閉資料庫使用shutdown abort關閉。

SYS@test> shutdown abort ;
ORACLE instance shut down.

SYS@test> startup mount
ORACLE instance started.
Total System Global Area 1603411968 bytes
Fixed Size                  2228784 bytes
Variable Size             973082064 bytes
Database Buffers          620756992 bytes
Redo Buffers                7344128 bytes
Database mounted.

2.在備庫執行：
SYS@testdg> ALTER SYSTEM FLUSH REDO TO 'test';
System altered.

--注意test要加引號，不然報錯：
SYS@testdg> ALTER SYSTEM FLUSH REDO TO test;
ALTER SYSTEM FLUSH REDO TO test
                           *
ERROR at line 1:
ORA-00922: missing or invalid option

$ oerr ora 922
00922, 00000, "missing or invalid option"
// *Cause:
// *Action:

--檢查alert*.log發現：

ALTER SYSTEM FLUSH REDO TO 'test' CONFIRM APPLY
Flush redo operation not allowed on a physical standby

--估計dg開在open read only模式，在active data guard狀態。啟動到mount狀態繼續測試：

SYS@testdg> shutdown immediate ;
Database closed.
Database dismounted.
ORACLE instance shut down.

SYS@testdg> startup mount
ORACLE instance started.
Total System Global Area 1603411968 bytes
Fixed Size                  2228784 bytes
Variable Size             905973200 bytes
Database Buffers          687865856 bytes
Redo Buffers                7344128 bytes
Database mounted.

SYS@testdg> ALTER SYSTEM FLUSH REDO TO 'test';
System altered.

--檢查alert*.log發現：

Mon Feb 22 16:37:01 2016
ALTER SYSTEM FLUSH REDO TO 'test' CONFIRM APPLY
Flush redo operation not allowed on a physical standby
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Using STANDBY_ARCHIVE_DEST parameter default value as /u01/app/oracle11g/archivelog
ALTER SYSTEM SET log_archive_trace=0 SCOPE=BOTH SID='testdg';
ALTER SYSTEM SET log_archive_format='%t_%s_%r.dbf' SCOPE=SPFILE SID='testdg';
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE  THROUGH ALL SWITCHOVER DISCONNECT  USING CURRENT LOGFILE
Attempt to start background Managed Standby Recovery process (testdg)
Mon Feb 22 16:37:04 2016
MRP0 started with pid=29, OS id=1006
MRP0: Background Managed Standby Recovery process started (testdg)
started logmerger process
Mon Feb 22 16:37:09 2016
Managed Standby Recovery starting Real Time Apply
Parallel Media Recovery started with 4 slaves
Waiting for all non-current ORLs to be archived...
All non-current ORLs have been archived.
Recovery of Online Redo Log: Thread 1 Group 5 Seq 4815 Reading mem 0
  Mem# 0: /u01/app/oracle11g/oradata/test/redostb02.log
Completed: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE  THROUGH ALL SWITCHOVER DISCONNECT  USING CURRENT LOGFILE
--注意看~,感覺還是不對。

3.感覺應該在主庫執行：
SYS@test> ALTER SYSTEM FLUSH REDO TO 'testdg';
System altered.

--檢查備庫的alert*.log:
Mon Feb 22 16:43:48 2016
Standby switchover readiness check: Checking whether recoveryapplied all redo..
Physical Standby applied all the redo from the primary.

--如果備庫開啟read only：

SYS@test> ALTER SYSTEM FLUSH REDO TO 'testdg';
ALTER SYSTEM FLUSH REDO TO 'testdg'
*
ERROR at line 1:
ORA-16447: Redo apply was not active at the target standby database

SYS@test> ALTER SYSTEM FLUSH REDO TO testdg;
ALTER SYSTEM FLUSH REDO TO testdg
                           *
ERROR at line 1:
ORA-00922: missing or invalid option
--必須加引號。

--說明原連結的介紹存在問題。