使用Flashback Query 恢复误删除的数据

bfhf5753

如果你在工作中误删除了一部分重要的数据，并且已经提交，当你需要恢复数据的时候，你可以登陆到数据库上仔细查看，如果是
Oracle
9iR2，你可以首先尝试使用flashback query闪回数据。
　　◆第一步：确认数据库的SCN变化：
SQL> col fscn for 9999999999999999999
SQL> col nscn for 9999999999999999999
SQL> select name,FIRST_CHANGE# fscn,NEXT_CHANGE# nscn,FIRST_TIME from
                                                         v$archived_log;
...................
NAME                               FSCN       NSCN FIRST_TIME
----------------------------     ---------   -------------------
/mwarch/oracle/1_52413.dbf     12929941968   12929942881 2005-06-22 14:38:28
/mwarch/oracle/1_52414.dbf     12929942881   12929943706 2005-06-22 14:38:32
/mwarch/oracle/1_52415.dbf     12929943706   12929944623 2005-06-22 14:38:35
/mwarch/oracle/1_52416.dbf     12929944623   12929945392 2005-06-22 14:38:38
/mwarch/oracle/1_52417.dbf     12929945392   12929945888 2005-06-22 14:38:41
/mwarch/oracle/1_52418.dbf     12929945888   12929945965 2005-06-22 14:38:44
/mwarch/oracle/1_52419.dbf     12929945965   12929948945 2005-06-22 14:38:45
/mwarch/oracle/1_52420.dbf     12929948945   12929949904 2005-06-22 14:46:05
/mwarch/oracle/1_52421.dbf     12929949904   12929950854 2005-06-22 14:46:08
/mwarch/oracle/1_52422.dbf     12929950854   12929951751 2005-06-22 14:46:11
/mwarch/oracle/1_52423.dbf     12929951751   12929952587 2005-06-22 14:46:14
...................
/mwarch/oracle/1_52498.dbf     12930138975   12930139212 2005-06-22 15:55:57
/mwarch/oracle/1_52499.dbf     12930139212   12930139446 2005-06-22 15:55:59
/mwarch/oracle/1_52500.dbf     12930139446   12930139682 2005-06-22 15:56:00
NAME                             FSCN           NSCN FIRST_TIME
-------------------------  -------------       -----------
/mwarch/oracle/1_52501.dbf     12930139682    12930139915 2005-06-22 15:56:02
/mwarch/oracle/1_52502.dbf     12930139915    12930140149 2005-06-22 15:56:03
/mwarch/oracle/1_52503.dbf     12930140149    12930140379 2005-06-22 15:56:05
/mwarch/oracle/1_52504.dbf     12930140379    12930140610 2005-06-22 15:56:05
/mwarch/oracle/1_52505.dbf     12930140610    12930140845 2005-06-22 15:56:07
14811 rows selected.
　　◆此时的SCN为：
SQL> select dbms_flashback.
get_system_change_number fscn from dual;
                FSCN
--------------------
         12930142214
　　◆此时使用应用用户尝试闪回
SQL> connect username/password
Connected.
　　◆现有的数据：
SQL> select count(*) from hs_passport;
  COUNT(*)
----------
    851998
　　◆创建恢复表
SQL> create table hs_passport_recov
as select * from hs_passport where 1=0;
Table created.
　　◆此处选择SCN向前恢复
SQL> select count(*) from hs_passport as of scn 12929970422;
  COUNT(*)
----------
    861686
　　◆尝试多个SCN，获取最佳值（注释：如果可以得知具体时间，那样则可以获得准确的数据闪回）
SQL> 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
SQL> /
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
SQL> /
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
SQL> /
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
　　◆注意：最后选择恢复到SCN为12929941968的时间点
SQL>
insert into hs_passport_recov
select * from hs_passport as of scn 12929941968;
861684 rows created.
SQL> commit;
Commit complete.
　　注释：至此，则可以满足需要，找回误删除的部分数据，闪回恢复成功。


本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u2/71105/showart_1001219.html