[Flashback]開啓數據庫閃回數據庫功能

Flashback是Oracle中一個重要的功能，想要使用閃回數據庫功能，須要將數據庫置於閃回數據庫的狀態。

1.檢查數據庫是否開啓歸檔狀態

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     25
Next log sequence to archive   27
Current log sequence           27

若是數據庫爲開啓歸檔模式

--關閉數據庫
SQL> shutdown immediate
--打開數據庫都mount階段
SQL> startup mount
--開啓歸檔模式
SQL> alter database archivelog;
--打開數據庫
SQL> alter database open;

2.檢查數據庫是否啓用數據庫閃回功能

SQL> select flashback_on from v$database;
 
FLASHBACK_ON
------------------
NO

3.修改db_recovery_file_dest、db_recovery_file_dest_size及db_flashback_retention_target三個參數內容
1)db_recovery_file_dest、db_recovery_file_dest_size兩個參數用於指定閃回日誌存放位置及最大大小。能夠根據具體環境作相應調整使用alter system set語句進行修改

SQL> show parameter db_recovery
 
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      /u01/oracle/fast_recovery_area
db_recovery_file_dest_size           big integer 4182M

2)查看db_flashback_retention_target保留時間

SQL> show parameter db_flashback
 
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_flashback_retention_target        integer     1440

4.啓動數據庫到mount階段

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
 
SQL> startup mount;
ORACLE instance started.
Total System Global Area  784998400 bytes
Fixed Size                  2257352 bytes
Variable Size             478154296 bytes
Database Buffers          301989888 bytes
Redo Buffers                2596864 bytes
Database mounted.

5.啓用flashback功能，並打開數據庫

--啓用flashback功能
SQL> alter database flashback on;
 
Database altered.
--打開數據庫
SQL> alter database open;
 
Database altered.

6.驗證閃回功能是否已開啓

SQL> select flashback_on from v$database;
 
FLASHBACK_ON
------------------
YES

 

來自：https://blog.csdn.net/u011364306/article/details/49249187