oracle閃回技術包括閃回刪除和閃回數據庫。閃回刪除主要是關注用戶誤刪除表、索引的數據庫對象；閃回數據庫是一種快速的數據庫恢復方案，這種恢復是基於用戶的邏輯錯誤，比如對錶中的數據做了錯誤的修改、插入了大量的錯誤數據。
[oracle@localhost ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.4.0 - Production on Mon Jun 9 16:50:00 2014
Copyright (c) 1982, 2007, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>
查看數據庫能閃回到的最早的scn，如果數據庫沒有開閃回功能是沒有記錄返回的。
SQL> select oldest_flashback_scn from v$flashback_database_log;
no rows selected
查看數據庫是否開閃回
SQL> select flashback_on from v$database;
FLASHBACK_ON
------------------
NO
數據庫open狀態嘗試開啓數據庫的閃回功能，返回報錯信息說明需要在mount狀態下來操作。
SQL> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-38759: Database must be mounted by only one instance and not open.
關閉數據庫
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
打開數據庫到mount狀態
SQL> startup mount
ORACLE instance started.
Total System Global Area 184549376 bytes
Fixed Size 1218412 bytes
Variable Size 83888276 bytes
Database Buffers 96468992 bytes
Redo Buffers 2973696 bytes
Database mounted.
數據庫在mount狀態下再次嘗試開啓數據庫的閃回功能，又返回錯誤信息說明數據庫在非歸檔狀態下不支持數據庫的閃回。
SQL> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-38706: Cannot turn on FLASHBACK DATABASE logging.
ORA-38707: Media recovery is not enabled.
開歸檔
SQL> alter database archivelog;
Database altered.
開閃回成功
SQL> alter database flashback on;
Database altered.
打開數據庫
SQL> alter database open;
Database altered.
開啓歸檔，默認的歸檔目錄：USE_DB_RECOVERY_FILE_DEST ，與9i不同10g開啓歸檔很要簡單一些。以後可以自行修改歸檔目錄的位置，在此暫時保留默認。
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 59
Next log sequence to archive 61
Current log sequence 61
檢驗數據庫閃回是否開啓
SQL> select flashback_on from v$database;
FLASHBACK_ON
------------------
YES
查看閃回區信息，默認安裝大小爲2G，根據數據庫的具體情況作修改。
SQL> show parameter recover_file_dest
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string /u01/app/oracle/flash_recovery_area
db_recovery_file_dest_size big integer 20G
數據庫可以恢復到多少分鐘以前，默認1440分鐘（一天）
SQL> show parameter flash
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_flashback_retention_target integer 1440
查看數據庫能恢復到最早的scn和最早的時間
SQL> select oldest_flashback_scn,oldest_flashback_time from v$flashback_database_log;
OLDEST_FLASHBACK_SCN OLDEST_FLASHBACK_TIME
-------------------- ---------------------
1021372 20101130 23:07:18
閃回刪除測試：
SQL*Plus: Release 10.2.0.4.0 - Production on Mon Jun 9 16:50:00 2014
Copyright (c) 1982, 2007, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> drop table student;
Table dropped.
SQL> show recyclebin;
ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME
---------------- ------------------------------ ------------ -------------------
STUDENT BIN$+2ROU1DktpLgQKjAkwBc6A==$0 TABLE 2014-06-09:16:50:41
SQL> select object_name,original_name,operation from recyclebin;
OBJECT_NAME
--------------------------------------------------------------------------------
ORIGINAL_NAME
--------------------------------------------------------------------------------
OPERATION
---------------------------
BIN$+2ROU1DltpLgQKjAkwBc6A==$0
STUDENT
DROP
SQL> select * from tab;
TNAME
--------------------------------------------------------------------------------
TABTYPE CLUSTERID
--------------------- ----------
BIN$+2ROU1DltpLgQKjAkwBc6A==$0
TABLE
SQL> flashback table student to before drop;
Flashback complete.
SQL> select * from tab;
TNAME
--------------------------------------------------------------------------------
TABTYPE CLUSTERID
--------------------- ----------
STUDENT
TABLE
SQL> select * from student;
SNO SNAME
---------- ------------------------------
1 xxx
11 aa
也可以執行下面語句進行閃回：
flashback table "BIN$+2ROU1DktpLgQKjAkwBc6A==$0" to before drop rename to student;
閃回數據庫測試
[oracle@localhost ~]$ sqlplus test/test
SQL*Plus: Release 10.2.0.4.0 - Production on Tue Jun 10 09:32:52 2014
Copyright (c) 1982, 2007, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> select * from student;
SNO SNAME
---------- ------------------------------
1 xxx
11 aa
[oracle@localhost ~]$ sqlplus sys/oracle as sysdba
SQL*Plus: Release 10.2.0.4.0 - Production on Tue Jun 10 09:34:32 2014
Copyright (c) 1982, 2007, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> select current_scn from v$database;
CURRENT_SCN
-----------
6312445
在test用戶下插入數據
SQL> insert into student values(22,'nn');
1 row created.
SQL> commit;
Commit complete.
然後在sys用戶下再查詢current_scn
SQL> /
CURRENT_SCN
-----------
6312458
通過v$flashback_database_log和v$flashback_database_stat視圖查詢相關閃回數據庫信息
SQL> select oldest_flashback_scn,oldest_flashback_time from v$flashback_database_log;
OLDEST_FLASHBACK_SCN OLDEST_FLASHBAC
-------------------- ---------------
6259583 09-JUN-14
SQL> select * from v$flashback_database_stat;
BEGIN_TIME END_TIME FLASHBACK_DATA DB_DATA REDO_DATA
--------------- --------------- -------------- ---------- ----------
ESTIMATED_FLASHBACK_SIZE
------------------------
10-JUN-14 10-JUN-14 5529600 7790592 2463744
關閉數據庫並啓動到mount狀態，執行閃回，並以resetlogs打開數據庫
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 1224736768 bytes
Fixed Size 2083560 bytes
Variable Size 335545624 bytes
Database Buffers 872415232 bytes
Redo Buffers 14692352 bytes
Database mounted.
SQL> flashback database to scn 6312445;
Flashback complete.
SQL> alter database open resetlogs;
Database altered.
1、使用sysdba身份登陸，可以查詢回收站裏所有的對象，也可以指定條件查詢
SQL> select object_name,original_name,operation from dba_recyclebin where original_name='STUDENT';
OBJECT_NAME
--------------------------------------------------------------------------------
ORIGINAL_NAME
--------------------------------------------------------------------------------
OPERATION
---------------------------
BIN$+2ROU1DltpLgQKjAkwBc6A==$0
STUDENT
DROP
2、無論是OS認證還是密碼認證，以sysdba登陸默認用戶是sys，sys用戶的默認表空間是system，system與sysaux表空間無法做回收站的操作
3、執行表閃回後，與表相關聯的對象也會被閃回，但是對象名已經發生變化，需要重命名或者重建對象
4、在閃回數據庫時，往往要用到具體的時間或者scn，我們可以定義容易記憶的復原點（scn的別名）來執行閃回，步驟如下
4.1、創建一個復原點
SQL> create restore point rp0;
Restore point created.
4.2、創建有保證的復原點
SQL> create restore point rp1 guarantee flashback database;
Restore point created.
4.3、查詢復原點信息
SQL> select name,scn,storage_size,guarantee_flashback_database from v$restore_point;
NAME
--------------------------------------------------------------------------------
SCN STORAGE_SIZE GUARANTEE
---------- ------------ ---------
RP1
6316026 31883264 YES
RP0
6322551 0 NO