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分类: 服务器与存储

2008-06-14 13:58:01

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。

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