Oracle 9i 開始支援閃回，Oracle10g開始全面支援閃回功能，Oracle11g有所完善，為大家快速的恢復資料，查詢歷史資料提供了很大的便捷方法。
本文主要對Oracle常用閃回使用做些詳細介紹，其中對於不常用的事務和版本閃回，這裡就不做介紹
一、Oracle閃回概述
| 閃回級別 | 閃回場景 | 閃回技術 | 物件依賴 | 影響資料 |
| 資料庫 | 表截斷、邏輯錯誤、其他多表意外事件 | 閃回DATABASE | 閃回日誌、undo | 是 |
| DROP | 刪除表 | 閃回DROP | 回收站(recyclebin) | 是 |
| 表 | 更新、刪除、插入記錄 | 閃回TABLE | 還原資料,undo | 是 |
| 查詢 | 當前資料和歷史資料對比 | 閃回QUERY | 還原資料,undo | 否 |
| 版本查詢 | 比較行版本 | 閃回Version Query | 還原資料,undo | 否 |
| 事務查詢 | 比較 | 閃回Transaction Query | 還原資料,undo | 否 |
| 歸檔 | DDL、DML | 閃回Archive | 歸檔日誌 | 是 |
二、Oracle閃回使用詳解
1、閃回開啟
(1)開啟閃回必要條件
a.開啟歸檔日誌
SQL> archive log list; Database log mode Archive Mode Automatic archival Enabled Archive destination /home/U01/app/oracle/oradata/testdb/arch Oldest online log sequence 844 Next log sequence to archive 846 Current log sequence 846 ##如未開啟，在mount狀態執行alter database archivelog;
b.設定合理的閃回區
db_recovery_file_dest：指定閃回恢復區的位置
db_recovery_file_dest_size：指定閃回恢復區的可用空間大小
db_flashback_retention_target：指定資料庫可以回退的時間，單位為分鐘，預設1440分鐘(1天),實際取決於閃回區大小
(2)檢查是否開啟閃回
SQL> select flashback_on from v$database; FLASHBACK_ON ------------------ NO
(3)開啟閃回
a.開啟歸檔
mount狀態：alter database archivelog;
b.設定閃回區
SQL> alter system set db_recovery_file_dest='/home/U01/app/oracle/fast_recovery_area' scope=both; System altered. SQL> alter system set db_recovery_file_dest_size=60G scope=both; System altered. SQL> alter system set db_flashback_retention_target=4320 scope=both; System altered.
c.開啟flashback (10g在mount開啟)
SQL> alter database flashback on; Database altered.
(4)確定閃回開啟
SQL> select flashback_on from v$database; FLASHBACK_ON ------------------ YES
(5)關閉閃回
SQL> alter database flashback off; Database altered.
2、閃回使用
(1)閃回查詢
閃回查詢主要是根據Undo表空間資料進行多版本查詢，針對v$和x$動態效能檢視無效，但對DBA_、ALL_、USER_是有效的
a.閃回查詢
允許使用者查詢過去某個時間點的資料，用以重構由於意外刪除或更改的資料，資料不會變化。
SQL> select * from scott.dept; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SQL> delete from scott.dept where deptno=40; 1 row deleted. SQL> commit; Commit complete. SQL> select * from scott.dept as of timestamp sysdate-10/1440; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SQL> select * from scott.dept as of timestamp to_timestamp('2017-12-14 16:20:00','yyyy-mm-dd hh24:mi:ss'); DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SQL> select * from scott.dept as of scn 16801523; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON
b.閃回版本查詢
用於查詢行級資料庫隨時間變化的方法
c.閃回事務查詢
用於提供檢視事務級別資料庫變化的方法
(2)閃回表(update/insert/delete)
閃回表就是對錶的資料做回退，回退到之前的某個時間點，其利用的是undo的歷史資料，與undo_retention設定有關，預設是14400分鐘（1天）
同樣，sys使用者表空間不支援閃回表,要想表閃回，需要允許表啟動行遷移(row movement)
閃回表示例：
SQL> flashback table scott.dept to timestamp to_timestamp('2017-12-14 16:20:00','yyyy-mm-dd hh24:mi:ss'); flashback table scott.dept to timestamp to_timestamp('2017-12-14 16:20:00','yyyy-mm-dd hh24:mi:ss') ERROR at line 1: ORA-08189: cannot flashback the table because row movement is not enabled SQL> select row_movement from dba_tables where table_name='DEPT' and owner='SCOTT'; ROW_MOVE -------- DISABLED SQL> alter table scott.dept enable row movement; Table altered. SQL> flashback table scott.dept to timestamp to_timestamp('2017-12-14 16:20:00','yyyy-mm-dd hh24:mi:ss'); Flashback complete. SQL> select * from scott.dept; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SQL> alter table scott.dept disable row movement; Table altered.
(3)閃回DROP(drop table)
當一個表被drop掉，表會被放入recyclebin回收站，可通過回收站做表的閃回。表上的索引、約束等同樣會被恢復
不支援sys/system使用者表空間物件，可通過alter system set recyclebin=off;關閉回收站功能
閃回DROP示例：
SQL> select * from t ; ID NAME ---------- --------------------------------------- 1 2 3 4 30 SQL> drop table t; Table dropped. SQL> show recyclebin; ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME ---------------- ------------------------------ ------------ ------------------- T BIN$YEh2QcvZdJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:02:06 SQL> flashback table t to before drop; Flashback complete. SQL> select * from t; ID NAME ---------- ------------------------------------- 1 2 3 4 30
備註：即使不開始flashback，只要開啟了recyclebin，那麼就可以閃回DROP表。
但如果連續覆蓋，就需要指定恢復的表名，如果已經存在表，則需要恢復重新命名。
SQL> show recyclebin; ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME ---------------- ------------------------------ ------------ ------------------- T BIN$YEh2QcvddJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:07:54 T BIN$YEh2QcvcdJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:07:27 SQL> flashback table "BIN$YEh2QcvcdJLgUxyAgQpnVQ==$0" to before drop ; Flashback complete. SQL> show recyclebin; ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME ---------------- ------------------------------ ------------ ------------------- T BIN$YEh2QcvddJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:07:54 SQL> flashback table t to before drop rename to tt; Flashback complete.
(4)閃回資料庫(truncate/多表資料變更)
資料庫閃回必須在mounted狀態下進行，基於快照的可以再open下進行閃回庫
閃回資料庫主要是將資料庫還原值過去的某個時間點或SCN，用於資料庫出現邏輯錯誤時，需要open database resetlogs
a.全庫閃回
資料庫閃回示例
SQL> select * from scott.EMP; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ---------- ---------- --------- ---------- ------------------- ---------- ---------- ---------- 7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20 7499 ALLEN SALESMAN 7698 1981-02-20 00:00:00 1600 300 30 7521 WARD SALESMAN 7698 1981-02-22 00:00:00 1250 500 30 7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 20 7654 MARTIN SALESMAN 7698 1981-09-28 00:00:00 1250 1400 30 7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30 7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10 7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20 7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10 7844 TURNER SALESMAN 7698 1981-09-08 00:00:00 1500 0 30 7876 ADAMS CLERK 7788 1987-05-23 00:00:00 1100 20 7900 JAMES CLERK 7698 1981-12-03 00:00:00 950 30 7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 20 7934 MILLER CLERK 7782 1982-01-23 00:00:00 1300 10 14 rows selected. SQL> truncate table scott.EMP; Table truncated. SQL> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started. Total System Global Area 9.4067E+10 bytes Fixed Size 2263936 bytes Variable Size 9395242112 bytes Database Buffers 8.4557E+10 bytes Redo Buffers 112766976 bytes Database mounted. SQL> flashback database to timestamp to_timestamp('2017-12-14 14:12:46','yyyy-mm-dd HH24:MI:SS'); Flashback complete. SQL> alter database open resetlogs; Database altered. SQL> select * from scott.emp; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ---------- ---------- --------- ---------- ------------------- ---------- ---------- ---------- 7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20 7499 ALLEN SALESMAN 7698 1981-02-20 00:00:00 1600 300 30 7521 WARD SALESMAN 7698 1981-02-22 00:00:00 1250 500 30 7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 20 7654 MARTIN SALESMAN 7698 1981-09-28 00:00:00 1250 1400 30 7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30 7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10 7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20 7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10 7844 TURNER SALESMAN 7698 1981-09-08 00:00:00 1500 0 30 7876 ADAMS CLERK 7788 1987-05-23 00:00:00 1100 20 7900 JAMES CLERK 7698 1981-12-03 00:00:00 950 30 7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 20 7934 MILLER CLERK 7782 1982-01-23 00:00:00 1300 10 14 rows selected.
b.快照閃回
針對主庫和備庫都可以建立閃回快照點，然後恢復到指定的快照點，但主庫一旦恢復到快照點，備庫的同步則需要重新同步
SQL> select * from scott.dept; DEPTNO DNAME LOC ADDR ---------- -------------- ------------- ------------------------------ 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO SQL> create restore point before_201712151111 guarantee flashback database; Restore point created. SQL> create table scott.t as select * from scott.dept; Table created. SQL> truncate table scott.t; Table truncated. SQL> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started. Total System Global Area 9.4067E+10 bytes Fixed Size 2263936 bytes Variable Size 9663677568 bytes Database Buffers 8.4289E+10 bytes Redo Buffers 112766976 bytes Database mounted. SQL> flashback database to restore point before_201712151111; Flashback complete. SQL> alter database open resetlogs; Database altered. 此時主庫scott.t已不存在： SQL> select * from scott.t; select * from scott.t * ERROR at line 1: ORA-00942: table or view does not exist 此時從庫的scott.依舊存在，主備同步終止 解決方案：在主庫建立快照時間點，從庫自動停止應用日誌，等主庫閃回後，重新應用日誌即可。 如果已經做了上述操作，從庫可以選擇重建 ALTER DATABASE REGISTER LOGFILE '/xx/xx/archive.dbf';
c.閃回snapshot standby
此功能在11GR2非常實用，可自動建立閃回點、開啟閃回日誌，可完成線上資料測試後，然後做資料庫閃回恢復主備關係
select scn, STORAGE_SIZE ,to_char(time,'yyyy-mm-dd hh24:mi:ss') time,NAME from v$restore_point; select database_role,open_mode,db_unique_name,flashback_on from v$database; SQL> set line 200; SQL> set pagesize 2000; SQL> select database_role,open_mode,db_unique_name,flashback_on from v$database; DATABASE_ROLE OPEN_MODE DB_UNIQUE_NAME FLASHBACK_ON ---------------- -------------------- ------------------------------ ------------------ PHYSICAL STANDBY READ ONLY testdbms NO SQL> ALTER DATABASE CONVERT TO SNAPSHOT STANDBY; Database altered. SQL> select database_role,open_mode,db_unique_name,flashback_on from v$database; DATABASE_ROLE OPEN_MODE DB_UNIQUE_NAME FLASHBACK_ON ---------------- -------------------- ------------------------------ ------------------ SNAPSHOT STANDBY MOUNTED testdbms RESTORE POINT ONLY SQL> alter database open; Database altered. SQL> select open_mode from v$database; OPEN_MODE -------------------- READ WRITE 此時備庫操作： SQL> select * from scott.emp; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ---------- ---------- --------- ---------- ------------------- ---------- ---------- ---------- 7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20 7499 ALLEN SALESMAN 7698 1981-02-20 00:00:00 1600 300 30 7521 WARD SALESMAN 7698 1981-02-22 00:00:00 1250 500 30 7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 20 7654 MARTIN SALESMAN 7698 1981-09-28 00:00:00 1250 1400 30 7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30 7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10 7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20 7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10 7844 TURNER SALESMAN 7698 1981-09-08 00:00:00 1500 0 30 7876 ADAMS CLERK 7788 1987-05-23 00:00:00 1100 20 7900 JAMES CLERK 7698 1981-12-03 00:00:00 950 30 7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 20 7934 MILLER CLERK 7782 1982-01-23 00:00:00 1300 10 14 rows selected. SQL> truncate table scott.emp; Table truncated. 主庫操作： SQL> create table scott.t as select * from scott.dept; Table created. SQL> select * from scott.t; DEPTNO DNAME LOC ADDR ---------- -------------- ------------- ------------------------------ 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 備庫恢復到物理standby SQL> shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started. Total System Global Area 9.4067E+10 bytes Fixed Size 2263936 bytes Variable Size 9663677568 bytes Database Buffers 8.4289E+10 bytes Redo Buffers 112766976 bytes Database mounted. SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY; Database altered. SQL> shutdown immediate; ORA-01507: database not mounted ORACLE instance shut down. SQL> startup ; ORACLE instance started. Total System Global Area 9.4067E+10 bytes Fixed Size 2263936 bytes Variable Size 9663677568 bytes Database Buffers 8.4289E+10 bytes Redo Buffers 112766976 bytes Database mounted. Database opened. ##此時備庫的資料已經恢復到轉變snapshot standby時間點 SQL> select database_role,open_mode,db_unique_name,flashback_on from v$database; DATABASE_ROLE OPEN_MODE DB_UNIQUE_NAME FLASHBACK_ON ---------------- -------------------- ------------------------------ ------------------ PHYSICAL STANDBY READ ONLY testdbms NO SQL> select * from scott.emp; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ---------- ---------- --------- ---------- ------------------- ---------- ---------- ---------- 7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20 7499 ALLEN SALESMAN 7698 1981-02-20 00:00:00 1600 300 30 7521 WARD SALESMAN 7698 1981-02-22 00:00:00 1250 500 30 7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 20 7654 MARTIN SALESMAN 7698 1981-09-28 00:00:00 1250 1400 30 7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30 7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10 7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20 7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10 7844 TURNER SALESMAN 7698 1981-09-08 00:00:00 1500 0 30 7876 ADAMS CLERK 7788 1987-05-23 00:00:00 1100 20 7900 JAMES CLERK 7698 1981-12-03 00:00:00 950 30 7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 20 7934 MILLER CLERK 7782 1982-01-23 00:00:00 1300 10 14 rows selected. SQL> alter database recover managed standby database using current logfile disconnect; Database altered. SQL> select * from scott.t; DEPTNO DNAME LOC ADDR ---------- -------------- ------------- ------------------------------ 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO SQL> select database_role,open_mode,db_unique_name,flashback_on from v$database; DATABASE_ROLE OPEN_MODE DB_UNIQUE_NAME FLASHBACK_ON ---------------- -------------------- ------------------------------ ------------------ PHYSICAL STANDBY READ ONLY WITH APPLY testdbms NO
(5)閃迴歸檔(增加、修改、重新命名、刪除表的列、truncate表、修改表的約束、以及修改分割槽表的分割槽規範)
3、閃回注意事項
(1)資料庫閃回需要在mounted下進行，並且open時需要使用resetlogs
(2)閃回DROP只能用於非系統表空間和本地管理的表空間，外來鍵約束無法恢復，對方覆蓋、重新命名需注意
(3)表DROP，對應的物化檢視會被徹底刪除，物化檢視不會存放在recyclebin裡
(4)閃回表，如果在做過dml，然後進行了表結構修改、truncate等DDL操作，新增/刪除結構無法做閃回
(5)閃迴歸檔，必須在assm管理tablespace和undo auto管理下進行
(6)注意閃回區管理，防止磁碟爆滿，閃回區空間不足等
(7)主庫做庫的閃回，會影響備庫，需要重新同步
(8)snapshot standby 不支援最高保護模式
三、備註
1、相關資料字典
V$FLASHBACK_DATABASE_LOG ##檢視資料庫可閃回的時間點/SCN等資訊
V$flashback_database_stat ##檢視閃回日誌空間記錄資訊
2、常用查詢語句
(1)檢視資料庫狀態
SQL> select NAME,OPEN_MODE ,DATABASE_ROLE,CURRENT_SCN,FLASHBACK_ON from v$database; NAME OPEN_MODE DATABASE_ROLE CURRENT_SCN FLASHBACK_ON ------------- -------------------- ---------------- ----------- ------------------ TESTDB READ WRITE PRIMARY 16812246 YES
(2)獲取當前資料庫的系統時間和SCN
SQL> select to_char(systimestamp,'yyyy-mm-dd HH24:MI:SS') as sysdt , dbms_flashback.get_system_change_number scn from dual; SYSDT SCN ------------------- ---------- 2017-12-14 14:28:33 16813234
(3)檢視資料庫可恢復的時間點
SQL> select * from V$FLASHBACK_DATABASE_LOG; OLDEST_FLASHBACK_SCN OLDEST_FLASHBACK_TI RETENTION_TARGET FLASHBACK_SIZE ESTIMATED_FLASHBACK_SIZE -------------------- ------------------- ---------------- -------------- ------------------------ 16801523 2017-12-14 11:35:05 4320 104857600 244113408
(4)檢視閃回日誌空間情況
SQL> select * from V$flashback_database_stat; BEGIN_TIME END_TIME FLASHBACK_DATA DB_DATA REDO_DATA ESTIMATED_FLASHBACK_SIZE ------------------- ------------------- -------------- ---------- ---------- ------------------------ 2017-12-14 14:34:53 2017-12-14 14:56:43 1703936 9977856 1487872 0
(5)SCN和timestamp裝換關係查詢
select scn,to_char(time_dp,'yyyy-mm-dd hh24:mi:ss')from sys.smon_scn_time;
(6)檢視閃回restore_point
select scn, STORAGE_SIZE ,to_char(time,'yyyy-mm-dd hh24:mi:ss') time,NAME from v$restore_point;
(7)閃回語句
a.閃回資料庫
FLASHBACK DATABASE TO TIMESTAMP to_timestamp('2017-12-14 14:28:33','yyyy-mm-dd HH24:MI:SS');;
flashback database to scn 16813234;
b.閃回DROP
其中table_name可以是刪除表名稱，也可以是別名
flashback table table_name to before drop;
flashback table table_name to before drop rename to table_name_new;
c.閃回表
flashback table table_name to scn scn_number;
flashback table table_name to timestamp to_timestamp('2017-12-14 14:28:33','yyyy-mm-dd hh24:mi:ss');
d.閃回查詢
select * from table_name as of timestamp to_timestamp('2017-12-14 14:28:33','yyyy-mm-dd hh24:mi:ss');
select * from scott.dept as of scn 16801523;
e.閃回快照
create restore point before_201712151111 guarantee flashback database;
flashback database to restore point before_201712151111;
(7)閃回空間爆滿問題處理
請參照我之前的微博：http://blog.itpub.net/27067062/viewspace-2129130/