Oracle误删除表数据后的数据恢复详解

发布时间：2016-11-27 18:28:55 所属栏目：大数据来源：网络整理

导读：Oracle误删除表数据后的恢复详解 nbsp; 测试环境： SYSTEM:IBM AIX 5Lnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; Oracle Version:10gR2 nbsp; 1. undo_retention参数的

Oracle误删除表数据后的恢复详解
nbsp;
测试环境：
SYSTEM:IBM AIX 5Lnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; Oracle Version:10gR2
nbsp;

1. undo_retention参数的查询与修改

使用show parameter undo命令查看当前的数据库参数undo_retention设置。
显示如下：
SQLgt; show parameter undo

NAMEnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; TYPEnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; VALUE
------------------------------------ ----------- ------------------------------
undo_managementnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; stringnbsp;nbsp;nbsp;nbsp;nbsp; AUTO
undo_retentionnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; integernbsp;nbsp;nbsp;nbsp; 900
undo_tablespacenbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; stringnbsp;nbsp;nbsp;nbsp;nbsp; UNDOTBS2
undo_retention(保持力)，900单位是秒，即15分钟。
修改默认的undo_retention参数设置：
SQLgt; ALTER SYSTEM SET undo_retention=10800 SCOPE=BOTH;

System altered.

SQLgt; show parameter undo

NAMEnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; TYPEnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; VALUE
------------------------------------ ----------- ------------------------------
undo_managementnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; stringnbsp;nbsp;nbsp;nbsp;nbsp; AUTO
undo_retentionnbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; integernbsp;nbsp;nbsp;nbsp; 10800
undo_tablespacenbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp;nbsp; stringnbsp;nbsp;nbsp;nbsp;nbsp; UNDOTBS2
undo_retention 10800，单位秒，即3小时。

2. oracle误删除表数据后的的快速恢复功能方法

2.1 方法一
通过oracle提供的回闪功能

exec dbms_flashback.enable_at_time(to_date('2011-04-15 08:21:00','yyyy-mm-dd hh24:mi:ss'));
set serveroutput on
DECLARE r_temp hr.job_history%ROWTYPE;
CURSOR c_temp IS SELECT * FROM hr.job_history;
BEGIN
OPEN c_temp;
dbms_flashback.disable;
LOOP
FETCH c_temp INTO r_temp;
EXIT WHEN c_temp%NOTFOUND;
insert into hr.job_history(EMPLOYEE_ID,JOB_ID,START_DATE,END_DATE) values (r_temp.EMPLOYEE_ID,r_temp.JOB_ID,r_temp.START_DATE,r_temp.END_DATE);
commit;
END LOOP;
CLOSE c_temp;
END;

这种办法可以将删除的数据恢复到对应的表中，首先要保证该用户有执行dbms_flashback包的权限。

2.2 方法二
insert into hr.job_history
select * from hr.job_history as of timestamp to_timestamp('2011-04-15 08:20:00', 'yyyy-mm-dd hh24:mi:ss');
这种方法简单，容易掌握，功能和上面的一样，此处的时间为你误操作之前的时间，最好是离误操作比较近的，因为oracle保存在回滚保持段里的数据时间有一定的时间限制，这个限制由undo_retention 这个参数值决定。

查看FIRST_CHANGE#,NEXT_CHANGE#,FIRST_TIME
SQLgt; set pagesize 9999
SQLgt; col fscn for 999999999
SQLgt; col nscn for 999999999
SQLgt; select name,FIRST_CHANGE# fscn,NEXT_CHANGE# nscn,FIRST_TIME from v$archived_log;

当前的SCN为:
SQLgt; select dbms_flashback.get_system_change_number fscn from dual;
nbsp;nbsp;nbsp;nbsp;nbsp; FSCN
----------
nbsp;nbsp; 3435958

使用应用用户尝试闪回
SQLgt; connect username/password
Connected.

现有数据:
SQLgt; select count(*) from hs_passport;
nbsp; COUNT(*)
----------
nbsp;nbsp;nbsp; 851998
创建恢复表：
SQLgt; create table hs_passport_recov as select * from hs_passport where 1=0;

Table created.

选择SCN向前恢复：
SQLgt; select count(*) from hs_passport as of scn 12929970422;
nbsp; COUNT(*)
----------
nbsp;nbsp;nbsp; 861686

尝试多个SCN，获取最佳值（如果能得知具体时间，那么可以获得准确的数据闪回）

SQLgt; select count(*) from hs_passport as of scn scn;
Enter value for scn: 12929941968
old  1: select count(*) from hs_passport as of scn scn
new  1: select count(*) from hs_passport as of scn 12929941968
 COUNT(*)
----------
  861684

SQLgt; /
Enter value for scn: 12927633776
old  1: select count(*) from hs_passport as of scn scn
new  1: select count(*) from hs_passport as of scn 12927633776
select count(*) from hs_passport as of scn 12927633776
           *
ERROR at line 1:
ORA-01466: unable to read data - table definition has changed

SQLgt; /
Enter value for scn: 12929928784
old  1: select count(*) from hs_passport as of scn scn
new  1: select count(*) from hs_passport as of scn 12929928784

 COUNT(*)
----------
  825110

SQLgt; /
Enter value for scn: 12928000000
old  1: select count(*) from hs_passport as of scn scn
new  1: select count(*) from hs_passport as of scn 12928000000
select count(*) from hs_passport as of scn 12928000000
           *
ERROR at line 1:
ORA-01466: unable to read data - table definition has changed

最后选择恢复到SCN为12929941968的时间点
SQLgt; insert into hs_passport_recov select * from hs_passport as of scn 12929941968;

861684 rows created.

SQLgt; commit;

Commit complete.

数据恢复简单例子
在过去，如果用户误删/更新了数据后，作为用户并没有什么直接的方法来进行恢复，他们必须求助DBA来对数据库进行恢复，到了Oracle9i，这一难堪的局面有所改善。Oracle 9i中提供了一项新的技术手段--闪回查询，用户使用闪回查询可以及时取得误操作前的数据，并可以针对错误进行相应的恢复措施，而这一切都无需DBA干预。

3. 下面我们通过一个例子来具体说明闪回查询的用法

示例
3.1 使用闪回查询前必须确定下面两个参数：
UNDO_MANAGEMENT = AUTO
undo_retention = 10800;
这个时间可以随便设，它表示在系统中保留提交了的UNDO信息的时间，10800就是保留3小时，即180分钟。
3.2 使用闪回查询

SQLgt; conn /as sysdba
Connected.
SQLgt; drop user lsf cascade;

User dropped.

SQLgt; create user lsf identified by lsf;

User created.

SQLgt; grant connect,resource to lsf;

Grant succeeded.

SQLgt; grant execute on dbms_flashback to lsf;

Grant succeeded.

SQLgt; conn lsf/lsf
Connected.
SQLgt; create table T(id int, name varchar2(20));

Table created.

SQLgt; insert into T values(1,'lsf');

1 row created.

SQLgt; insert into T values(2,'lsf');

1 row created.

SQLgt; insert into T values(3,'lsf');

1 row created.

SQLgt; commit;

Commit complete.

SQLgt; select * from T;

    ID NAME
---------- ------------------------------------------------------------
     1 lsf
     2 lsf
     3 lsf

SQLgt; set time on
10:12:50 SQLgt; delete from T where id=1;

1 row deleted.

10:13:02 SQLgt; commit;

Commit complete.

10:13:10 SQLgt; select * from T;

    ID NAME
---------- ------------------------------------------------------------
     2 lsf
     3 lsf

10:13:18 SQLgt; execute DBMS_FLASHBACK.ENABLE_AT_TIME(to_date('2011-04-15 10:12:50','YYYY-MM-DD HH24:MI:SS'));

PL/SQL procedure successfully completed.

10:13:50 SQLgt; select * from T;

    ID NAME
---------- ------------------------------------------------------------
     1 lsf
     2 lsf
     3 lsf

10:13:57 SQLgt; execute DBMS_FLASHBACK.DISABLE;

PL/SQL procedure successfully completed.

10:15:48 SQLgt; select * from T;

    ID NAME
---------- ------------------------------------------------------------
     2 lsf
     3 lsf

3.3 使用闪回查询恢复数据

10:16:59 SQLgt; truncate table T;

Table truncated.

10:18:15 SQLgt; select * from T;

no rows selected

10:18:22 SQLgt; insert into T values(1,'lsf');

1 row created.

10:19:42 SQLgt; insert into T values(2,'lsf');

1 row created.

10:19:48 SQLgt; insert into T values(3,'lsf');

1 row created.

10:19:55 SQLgt; insert into T values(4,'lsf');

1 row created.

10:20:07 SQLgt; insert into T values(5,'lsf');

1 row created.

10:20:15 SQLgt; insert into T values(6,'lsf');

1 row created.

10:20:21 SQLgt; commit;

Commit complete.

10:20:26 SQLgt; select * from T;

    ID NAME
---------- ------------------------------------------------------------
     1 lsf
     2 lsf
     3 lsf
     4 lsf
     5 lsf
     6 lsf

6 rows selected.

10:20:56 SQLgt; delete T;

6 rows deleted.

10:21:27 SQLgt; commit;

Commit complete.

10:21:40 SQLgt; declare
10:22:29  2 cursor flash_recover is
10:22:43  3 select * from T;
10:22:50  4 t_recode T%rowtype;
10:23:11  5 begin
10:23:14  6 DBMS_FLASHBACK.ENABLE_AT_TIME(to_date('2011-04-15 10:20:56','YYYY-MM-DD HH24:MI:SS'));
10:24:22  7 open flash_recover;
10:24:39  8 DBMS_FLASHBACK.DISABLE;
10:24:59  9 loop
10:25:05 10 FETCH flash_recover into t_recode;
10:25:24 11 EXIT WHEN flash_recover%NOTFOUND;
10:25:45 12 insert into T values(t_recode.id,t_recode.name);
10:26:35 13 end loop;
10:26:39 14 CLOSE FLASH_RECOVER;
10:26:50 15 commit;
10:26:56 16 end;
10:26:58 17 /

PL/SQL procedure successfully completed.

10:27:00 SQLgt; select * from T;

    ID NAME
---------- ------------------------------------------------------------
     1 lsf
     2 lsf
     3 lsf
     4 lsf
     5 lsf
     6 lsf

6 rows selected.

我们可以已经恢复了所有的6条纪录，但是由于闪回查询的局限性，有可能不能恢复所有的6条记录，原因就在下面。

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