教你轻松掌握恢复误删除的数据的好方法
来源：岁月联盟
时间：2008-01-28
假如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，假如是Oracle9iR2，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 9999999999999999999SQL> col nscn for 9999999999999999999SQL> 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 15:56:00NAME 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 15:56:0714811 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/passwordConnected. |
◆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：假如可以得知具体时间，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: 12929941968old 1: select count(*) from hs_passport as of scn &scnnew 1: select count(*) from hs_passport as of scn 12929941968 COUNT(*)---------- 861684SQL> /Enter value for scn: 12927633776old 1: select count(*) from hs_passport as of scn &scnnew 1: select count(*) from hs_passport as of scn 12927633776select count(*) from hs_passport as of scn 12927633776 *ERROR at line 1:ORA-01466: unable to read data - table definition has changedSQL> /Enter value for scn: 12929928784old 1: select count(*) from hs_passport as of scn &scnnew 1: select count(*) from hs_passport as of scn 12929928784 COUNT(*)---------- 825110SQL> /Enter value for scn: 12928000000old 1: select count(*) from hs_passport as of scn &scnnew 1: select count(*) from hs_passport as of scn 12928000000select count(*) from hs_passport as of scn 12928000000 *ERROR at line 1:ORA-01466: unable to read data - table definition has changed |
◆注重：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。
