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Oracle Flashback Query 闪回数据

时间:2018-06-04  来源:未知  作者:admin666

误删除了Oracle部分重要数据,已提交,需要恢复。首先尝试Flashback Query闪回数据。

数据库运行在归档模式,首先确认数据库的SCN的变化:

SQL> col fscn for 999999999999999999999
SQL> col nscn for 999999999999999999999
SQL> select name,first_change# fscn,next_change# nscn, first_time from v$archived_log;

NAME                                            FSCN    NSCN FIRST_TIME
----------------------------------------------------------------------------- ----------- ----------- ------------------
/u01/app/oracle/fast_recovery_area/CDB/CDB/archivelog/2018_05_28/o1_mf_1_3_fj      1547949    1550763 2018:05:2816:37:41
qj6z9t_.arc

/u01/app/oracle/fast_recovery_area/CDB/CDB/archivelog/2018_05_28/o1_mf_1_4_fj      1550763    1551171 2018:05:2816:42:07
qjsm3t_.arc

/u01/app/oracle/fast_recovery_area/CDB/CDB/archivelog/2018_05_28/o1_mf_1_5_fj      1551171    1551255 2018:05:2816:52:03
qjwkog_.arc

/u01/app/oracle/fast_recovery_area/CDB/CDB/archivelog/2018_05_28/o1_mf_1_6_fj      1551255    1551654 2018:05:2816:53:37
qjxycd_.arc

获取当前的SCN:
SQL> select dbms_flashback.get_system_change_number  fscn from dual;

          FSCN
----------------------
          1551702       

使用应用用户尝试闪回:
SQL> conn c##scott/tiger
Connected.

现有数据:
SQL> select count(*) from emp1;

  COUNT(*)
----------
    0

创建恢复表:
SQL> create table emp1_recov as select * from emp1 where 1=0;

Table created.

根据业务提供的大致误操作时间,结合V$ARCHIVED_LOG视图,选择适当SCN向前执行闪回查询:
 
SQL> select count(*) from emp1 as of scn 1551171;
select count(*) from emp1 as of scn 1551171
                    *
ERROR at line 1:
ORA-01466: unable to read data - table definition has changed

尝试多个SCN,获取最佳值(能知道具体时间,那么可以获取准确的数据恢复):

SQL> select count(*) from emp1 as of scn 1551255;

  COUNT(*)
----------
    14

SQL> select count(*) from emp1 as of scn 1551200;
select count(*) from emp1 as of scn 1551200
                    *
ERROR at line 1:
ORA-01466: unable to read data - table definition has changed


SQL> select count(*) from emp1 as of scn 1551233;
select count(*) from emp1 as of scn 1551233
                    *
ERROR at line 1:
ORA-01466: unable to read data - table definition has changed


SQL> select count(*) from emp1 as of scn 1551244;

  COUNT(*)
----------
    14

最后选择恢复到SCN为1551244的时间点,代码如下:
SQL> insert into emp1_recov select * from emp1 as of scn 1551244;

14 rows created.

SQL> commit;

Commit complete.

由业务人员通过emp1_recov表确认,向当前表补回误删除的数据,至此闪回恢复成功。没有闪回特性的话,需要通过物理备份执行不完全恢复,或者找出足够及时的逻辑备份来进行恢复,其过程都可能是极其复杂的。

更多Oracle相关信息见Oracle 专题页面 https://www.linuxidc.com/topicnews.aspx?tid=12

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