Oracle误删除表数据后的数据恢复详解

Oracle误删除表数据后的恢复详解
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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
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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.

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