Oracle 9i 开始支持闪回，Oracle10g开始全面支持闪回功能，Oracle11g有所完善，为大家快速的恢复数据，查询历史数据提供了很大的便捷方法。

本文主要对Oracle常用闪回使用做些详细介绍，其中对于不常用的事务和版本闪回，这里就不做介绍

一、Oracle闪回概述

闪回级别

闪回场景

闪回技术

对象依赖

影响数据

数据库

表截断、逻辑错误、其他多表意外事件

闪回DATABASE

闪回日志、undo

是

DROP

删除表

闪回DROP

回收站(recyclebin)

是

表

更新、删除、插入记录

闪回TABLE

还原数据,undo

是

查询

当前数据和历史数据对比

闪回QUERY

还原数据,undo

否

版本查询

比较行版本

闪回Version Query

还原数据,undo

否

事务查询

比较

闪回Transaction Query

还原数据,undo

否

归档

DDL、DML

闪回Archive

归档日志

是

二、Oracle闪回使用详解

1、闪回开启

(1)开启闪回必要条件

a.开启归档日志

SQL> archive loglist;Database logmode Archive Mode

Automatic archival Enabled

Archive destination/home/U01/app/oracle/oradata/testdb/arch

Oldest onlinelog sequence 844

Next log sequence to archive 846

Current log sequence 846##如未开启，在mount状态执行alterdatabase archivelog;

b.设置合理的闪回区

db_recovery_file_dest：指定闪回恢复区的位置

db_recovery_file_dest_size：指定闪回恢复区的可用空间大小

db_flashback_retention_target：指定数据库可以回退的时间，单位为分钟，默认1440分钟(1天),实际取决于闪回区大小

(2)检查是否开启闪回

SQL> select flashback_on from v$database;

FLASHBACK_ON------------------

NO

(3)开启闪回

a.开启归档

mount状态：alter database archivelog;

b.设置闪回区

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.开启flashback (10g在mount开启)

SQL> alter database flashback on;Database altered.

(4)确定闪回开启

SQL> select flashback_on from v$database;

FLASHBACK_ON------------------

YES

(5)关闭闪回

SQL> alter database flashback off;Database altered.

2、闪回使用

(1)闪回查询

闪回查询主要是根据Undo表空间数据进行多版本查询，针对v$和x$动态性能视图无效，但对DBA_、ALL_、USER_是有效的

a.闪回查询

允许用户查询过去某个时间点的数据，用以重构由于意外删除或更改的数据，数据不会变化。

SQL> select * fromscott.dept;

DEPTNO DNAME LOC---------- -------------- -------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES CHICAGO40OPERATIONS BOSTON

SQL> delete from scott.dept where deptno=40;1row deleted.

SQL> commit;Commitcomplete.

SQL> select * from scott.dept as of timestamp sysdate-10/1440;

DEPTNO DNAME LOC---------- -------------- -------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES CHICAGO40OPERATIONS 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---------- -------------- -------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES CHICAGO40OPERATIONS BOSTON

SQL> select * from scott.dept as of scn 16801523;

DEPTNO DNAME LOC---------- -------------- -------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES CHICAGO40 OPERATIONS BOSTON

b.闪回版本查询

用于查询行级数据库随时间变化的方法

c.闪回事务查询

用于提供查看事务级别数据库变化的方法

(2)闪回表(update/insert/delete)

闪回表就是对表的数据做回退，回退到之前的某个时间点，其利用的是undo的历史数据，与undo_retention设置有关，默认是14400分钟(1天)

同样，sys用户表空间不支持闪回表,要想表闪回，需要允许表启动行迁移(row movement)

闪回表示例：

SQL> flashback table scott.dept to timestamp to_timestamp('2017-12-14 16:20:00','yyyy-mm-dd hh24:mi:ss');

flashbacktable scott.dept to timestamp to_timestamp('2017-12-14 16:20:00','yyyy-mm-dd hh24:mi:ss')

ERROR at line1:

ORA-08189: cannot flashback the table because row movement is notenabled

SQL> select row_movement from dba_tables where table_name='DEPT' and owner='SCOTT';

ROW_MOVE--------

DISABLED

SQL> alter tablescott.dept enable row movement;Tablealtered.

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 * fromscott.dept;

DEPTNO DNAME LOC---------- -------------- -------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES CHICAGO40OPERATIONS BOSTON

SQL> alter tablescott.dept disable row movement;Table altered.

(3)闪回DROP(drop table)

当一个表被drop掉，表会被放入recyclebin回收站，可通过回收站做表的闪回。表上的索引、约束等同样会被恢复

不支持sys/system用户表空间对象，可通过alter system set recyclebin=off;关闭回收站功能

闪回DROP示例：

SQL> select * fromt ;

ID NAME---------- ---------------------------------------

1

2

3

4

30SQL> drop tablet;Tabledropped.

SQL>show recyclebin;

ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPEDROPTIME---------------- ------------------------------ ------------ -------------------

T BIN$YEh2QcvZdJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:02:06SQL> flashback table t to before drop;

Flashback complete.

SQL> select * fromt;

ID NAME---------- -------------------------------------

1

2

3

4

30

备注：即使不开始flashback，只要开启了recyclebin，那么就可以闪回DROP表。

但如果连续覆盖，就需要指定恢复的表名，如果已经存在表，则需要恢复重命名。

SQL>show recyclebin;

ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPEDROPTIME---------------- ------------------------------ ------------ -------------------

T BIN$YEh2QcvddJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:07:54T BIN$YEh2QcvcdJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:07:27SQL> flashback table "BIN$YEh2QcvcdJLgUxyAgQpnVQ==$0" to before drop;

Flashback complete.

SQL>show recyclebin;

ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPEDROPTIME---------------- ------------------------------ ------------ -------------------

T BIN$YEh2QcvddJLgUxyAgQpnVQ==$0 TABLE 2017-12-14:15:07:54SQL> flashback table t to before drop rename tott;

Flashback complete.

(4)闪回数据库(truncate/多表数据变更)

数据库闪回必须在mounted状态下进行，基于快照的可以再open下进行闪回库

闪回数据库主要是将数据库还原值过去的某个时间点或SCN，用于数据库出现逻辑错误时，需要open database resetlogs

a.全库闪回

数据库闪回示例

SQL> select * fromscott.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

14rows selected.

SQL> truncate tablescott.EMP;Tabletruncated.

SQL> shutdownimmediate;Databaseclosed.Databasedismounted.

ORACLE instance shut down.

SQL>startup mount;

ORACLE instance started.

Total System Global Area9.4067E+10bytes

Fixed Size2263936bytes

Variable Size9395242112bytesDatabase Buffers 8.4557E+10bytes

Redo Buffers112766976bytesDatabasemounted.

SQL> flashback database to timestamp to_timestamp('2017-12-14 14:12:46','yyyy-mm-dd HH24:MI:SS');

Flashback complete.

SQL> alter database openresetlogs;Databasealtered.

SQL> select * fromscott.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.快照闪回

针对主库和备库都可以创建闪回快照点，然后恢复到指定的快照点，但主库一旦恢复到快照点，备库的同步则需要重新同步

SQL> select * fromscott.dept;

DEPTNO DNAME LOC ADDR---------- -------------- ------------- ------------------------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES CHICAGO

SQL> create restore point before_201712151111 guarantee flashback database;Restorepoint created.

SQL> create table scott.t as select * fromscott.dept;Tablecreated.

SQL> truncate tablescott.t;Tabletruncated.

SQL> shutdownimmediate;Databaseclosed.Databasedismounted.

ORACLE instance shut down.

SQL>startup mount;

ORACLE instance started.

Total System Global Area9.4067E+10bytes

Fixed Size2263936bytes

Variable Size9663677568bytesDatabase Buffers 8.4289E+10bytes

Redo Buffers112766976bytesDatabasemounted.

SQL> flashback database to restorepoint before_201712151111;

Flashback complete.

SQL> alter database openresetlogs;Databasealtered.

此时主库scott.t已不存在：

SQL> select * fromscott.t;select * fromscott.t*ERROR at line1:

ORA-00942: table or view does notexist

此时从库的scott.依旧存在，主备同步终止

解决方案：在主库创建快照时间点，从库自动停止应用日志，等主库闪回后，重新应用日志即可。

如果已经做了上述操作，从库可以选择重建ALTER DATABASE REGISTER LOGFILE '/xx/xx/archive.dbf';

c.闪回snapshot standby

此功能在11GR2非常实用，可自动创建闪回点、开启闪回日志，可完成线上数据测试后，然后做数据库闪回恢复主备关系

select scn, STORAGE_SIZE ,to_char(time,'yyyy-mm-dd hh24:mi:ss') time,NAME fromv$restore_point;select database_role,open_mode,db_unique_name,flashback_on from v$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 ONLYtestdbms NO

SQL> ALTER DATABASE CONVERT TOSNAPSHOT STANDBY;Databasealtered.

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 ONLYSQL> alter database open;Databasealtered.

SQL> select open_mode from v$database;

OPEN_MODE--------------------

READWRITE

此时备库操作：

SQL> select * fromscott.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

14rows selected.

SQL> truncate tablescott.emp;Tabletruncated.

主库操作：

SQL> create table scott.t as select * fromscott.dept;Tablecreated.

SQL> select * fromscott.t;

DEPTNO DNAME LOC ADDR---------- -------------- ------------- ------------------------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES CHICAGO

备库恢复到物理standby

SQL> shutdownimmediate;Databaseclosed.Databasedismounted.

ORACLE instance shut down.

SQL>startup mount;

ORACLE instance started.

Total System Global Area9.4067E+10bytes

Fixed Size2263936bytes

Variable Size9663677568bytesDatabase Buffers 8.4289E+10bytes

Redo Buffers112766976bytesDatabasemounted.

SQL> ALTER DATABASE CONVERT TOPHYSICAL STANDBY;Databasealtered.

SQL> shutdownimmediate;

ORA-01507: database notmounted

ORACLE instance shut down.

SQL>startup ;

ORACLE instance started.

Total System Global Area9.4067E+10bytes

Fixed Size2263936bytes

Variable Size9663677568bytesDatabase Buffers 8.4289E+10bytes

Redo Buffers112766976bytesDatabasemounted.Databaseopened.

##此时备库的数据已经恢复到转变snapshot standby时间点

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 ONLYtestdbms NO

SQL> select * fromscott.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

14rows selected.

SQL> alter database recover managed standby database using currentlogfile disconnect;Databasealtered.

SQL> select * fromscott.t;

DEPTNO DNAME LOC ADDR---------- -------------- ------------- ------------------------------

10ACCOUNTING NEW YORK20RESEARCH DALLAS30SALES 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 WITHAPPLY testdbms NO

(5)闪回归档(增加、修改、重命名、删除表的列、truncate表、修改表的约束、以及修改分区表的分区规范)

3、闪回注意事项

(1)数据库闪回需要在mounted下进行，并且open时需要使用resetlogs

(2)闪回DROP只能用于非系统表空间和本地管理的表空间，外键约束无法恢复，对方覆盖、重命名需注意

(3)表DROP，对应的物化视图会被彻底删除，物化视图不会存放在recyclebin里

(4)闪回表，如果在做过dml，然后进行了表结构修改、truncate等DDL操作，新增/删除结构无法做闪回

(5)闪回归档，必须在assm管理tablespace和undo auto管理下进行

(6)注意闪回区管理，防止磁盘爆满，闪回区空间不足等

(7)主库做库的闪回，会影响备库，需要重新同步

(8)snapshot standby 不支持最高保护模式

三、备注

1、相关数据字典

V$FLASHBACK_DATABASE_LOG ##查看数据库可闪回的时间点/SCN等信息

V$flashback_database_stat ##查看闪回日志空间记录信息

2、常用查询语句

(1)查看数据库状态

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)获取当前数据库的系统时间和SCN

SQL> select to_char(systimestamp,'yyyy-mm-dd HH24:MI:SS') as sysdt , dbms_flashback.get_system_change_number scn fromdual;

SYSDT SCN------------------- ----------

2017-12-14 14:28:33 16813234

(3)查看数据库可恢复的时间点

SQL> select * fromV$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)查看闪回日志空间情况

SQL> select * fromV$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装换关系查询

select scn,to_char(time_dp,'yyyy-mm-dd hh24:mi:ss')from sys.smon_scn_time;

(6)查看闪回restore_point

select scn, STORAGE_SIZE ,to_char(time,'yyyy-mm-dd hh24:mi:ss') time,NAME from v$restore_point;

(7)闪回语句

a.闪回数据库

FLASHBACK DATABASE TO TIMESTAMP to_timestamp('2017-12-14 14:28:33','yyyy-mm-dd HH24:MI:SS');;

flashback database to scn 16813234;

b.闪回DROP

其中table_name可以是删除表名称，也可以是别名

flashback table table_name to before drop;

flashback table table_name to before drop rename to table_name_new;

c.闪回表

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.闪回查询

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.闪回快照

create restore point before_201712151111 guarantee flashback database;

flashback database to restore point before_201712151111;

(7)闪回空间爆满问题处理