oracle 9iR2的具体表的闪回功能

注意：9i 的scn与时间的同步问题，需要5分钟以后才能同步，也就是说，如果新插入的数据，还不到5分钟，马上就根据时间来flashback query，是查不到数据的

 

下午接到研发工程师的电话，说误删除了部分重要数据，并且已经提交，需要恢复。

登陆到数据库上查看，由于是Oracle9iR2，首先尝试使用flashback query闪回数据。

首先确认数据库的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.

当前的SCN为:

SQL> select dbms_flashback.get_system_change_number fscn from dual;

                FSCN
--------------------
         12930142214

使用应用用户尝试闪回

SQL> connect username/password
Connected.

现有数据:

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.

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（如果能得知具体时间，那么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

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.

研发人员确认，已经可以满足需要，找回误删除部分数据，至此闪回恢复成功完成。

 

还有第二个修改方法：

SELECT * FROM table AS OF TIMESTAMP (to_timestamp('20051108 08:00:33','yyyymmdd hh24:mi:ss'));