使用bbed修改文件头，推进scn，恢复offline drop的数据文件

最近处理了一起由于用户操作错误导致的数据库无法打开的情况。

用户数据库为windows 64bit，数据库版本为11.2.0.1，非归档模式。由于异常断电，数据库无法正常打开，而且经过用户的判断使用了错误的offline drop操作。导致数据库打开后，日志文件切换过多，无法使用recover命令。
因为中间没有做其他操作，所以接到case后，这里将受损的几个数据文件copy到linux下使用bbed进行修改，再copy回windows，成功跳过recover，打开了offline drop的数据文件。

情景还原：

sys@UTF8A> select name ,checkpoint_change# from v$datafile ;
 
NAME                                              CHECKPOINT_CHANGE#
--------------------------------------------------------------------
/u01/apps/oracle/oradata/utf8a/system01.dbf                   1040256
/u01/apps/oracle/oradata/utf8a/sysaux01.dbf                   1040256
/u01/apps/oracle/oradata/utf8a/undotbs01.dbf                  1040256
/u01/apps/oracle/oradata/utf8a/users01.dbf                    1039896
 
 
sys@UTF8A> select sequence#, group#,first_change#,statusfrom v$log ;
 
 SEQUENCE#    GROUP# FIRST_CHANGE# STATUS
---------- ---------- -----------------------------
       19          1       1040256 CURRENT
       17          2       1040250 INACTIVE
       18          3       1040253 INACTIVE
 
 
sys@UTF8A> recover datafile 4  ;
ORA-00279: change 1039896 generated at03/30/2015 09:31:05 needed for thread 1
ORA-00289: suggestion :/u01/apps/oracle/product/11.2.0/dbhome_1/dbs/arch1_12_827004096.dbf
ORA-00280: change 1039896 for thread 1 isin sequence #12
 
 
Specify log: {<RET>=suggested |filename | AUTO | CANCEL}
auto
ORA-00308: cannot open archived log'/u01/apps/oracle/product/11.2.0/dbhome_1/dbs/arch1_12_827004096.dbf'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file ordirectory
Additional information: 3
 
 
ORA-00308: cannot open archived log'/u01/apps/oracle/product/11.2.0/dbhome_1/dbs/arch1_12_827004096.dbf'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file ordirectory
Additional information: 3

sequence已经过去，无法执行恢复，所以这里只能使用bbed修改文件头了。归档以及备份真的很重要。

block为8192。
flist：

1/u01/apps/oracle/oradata/utf8a/system01.dbf 754974720
2/u01/apps/oracle/oradata/utf8a/sysaux01.dbf 566231040
3/u01/apps/oracle/oradata/utf8a/undotbs01.dbf 83886080
4/u01/apps/oracle/oradata/utf8a/users01.dbf 9175040


如何初始化bbed环境，以及各种bbed版本的下载，见我的博客
/article/1539403.html

这里不再重复赘述。


先关闭数据库并且启动到mount状态。

sys@UTF8A> selectfile#,change#,online_status from v$recover_file ;
 
    FILE#    CHANGE# ONLINE_
---------- ---------- -------
        4    1039896 OFFLINE
 
sys@UTF8A> select name ,checkpoint_change# from v$datafile ;
 
NAME                                              CHECKPOINT_CHANGE#
--------------------------------------------------------------------
/u01/apps/oracle/oradata/utf8a/system01.dbf                   1041564
/u01/apps/oracle/oradata/utf8a/sysaux01.dbf                   1041564
/u01/apps/oracle/oradata/utf8a/undotbs01.dbf                  1041564
/u01/apps/oracle/oradata/utf8a/users01.dbf                    1039896

记得修改前先备份所有的数据库文件。

BBED> set file 4
       FILE#           4
 
BBED> p kcvfhckp
struct kcvfhckp, 36 bytes                   @484    
  struct kcvcpscn, 8 bytes                @484    
      ub4 kscnbas                           @484      0x000fde18
     ub2 kscnwrp                          @488      0x0000
  ub4 kcvcptim                            @492      0x34321859
  ub2 kcvcpthr                            @496      0x0001
  union u, 12 bytes                       @500    
     struct kcvcprba, 12 bytes            @500    
        ub4 kcrbaseq                      @500      0x0000000c
        ub4 kcrbabno                      @504      0x00000015
        ub2 kcrbabof                      @508      0x0010
  ub1 kcvcpetb[0]                          @512      0x02
  ub1 kcvcpetb[1]                         @513      0x00
  ub1 kcvcpetb[2]                         @514      0x00
  ub1 kcvcpetb[3]                         @515      0x00
  ub1 kcvcpetb[4]                         @516      0x00
  ub1 kcvcpetb[5]                         @517      0x00
  ub1 kcvcpetb[6]                         @518      0x00
  ub1 kcvcpetb[7]                         @519      0x00

注意offset 484 ， kscnbas为数据文件现在的scn。
使用计算器计算后0x000fde18，得到的十进制数字为1039896，确认无误，只要修改scn为最新的1041564，即可打开损坏的数据文件。

BBED> d /v dba 4,1 offset 484 count 16
 File: /u01/apps/oracle/oradata/utf8a/users01.dbf(4)
 Block: 1      Offsets:  484 to  499 Dba:0x01000001
-------------------------------------------------------
 18de0f00 00000000 59183234 01000000 l ......Y.24....
 
 <16 bytes per line>

因为是这里为linux x64 ，为little endian。
1039896=18de0f00
1041564=9ce40f00


直接修改即可。

BBED> set mode edit
       MODE            Edit
 
BBED> m /x 9ce40f dba 4,1 offset 484
 File:/u01/apps/oracle/oradata/utf8a/users01.dbf (4)
 Block: 1                Offsets:  484 to 499           Dba:0x01000001
------------------------------------------------------------------------
 9ce40f00 00000000 59183234 01000000
 
 <32 bytes per line>
 
 
 
BBED> m /x 9ce40f dba 4,1 offset 484
 File: /u01/apps/oracle/oradata/utf8a/users01.dbf(4)
 Block: 1                Offsets:  484 to 499           Dba:0x01000001
------------------------------------------------------------------------
 9ce40f00 00000000 59183234 01000000
 
 <32 bytes per line>
 
BBED> sum
Check value for File 4, Block 1:
current = 0x5f67, required = 0x65e3
 
BBED> sum apply
Check value for File 4, Block 1:
current = 0x65e3, required = 0x65e3

完成任务

sys@UTF8A> alter database datafile 4online ;
 
Database altered.
 
sys@UTF8A> selectfile#,change#,online_status from v$recover_file ;
 
    FILE#    CHANGE# ONLINE_
---------- ---------- -------
        4    1041564 ONLINE
 
sys@UTF8A> alter database datafile 4online ;
 
Database altered.
 
sys@UTF8A> alter database open ;
alter database open
*
ERROR at line 1:
ORA-01113: file 4 needs media recovery
ORA-01110: data file 4:'/u01/apps/oracle/oradata/utf8a/users01.dbf'
 
 
sys@UTF8A> recover datafile 4 ;
Media recovery complete.
sys@UTF8A> alter database open ;
 
Database altered.
 
sys@UTF8A> select * from scott.emp where rownum<2 ;
 
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM    DEPTNO
---------- ---------- --------- ---------- --------- -------------------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20

完成后记得逻辑导出所有用户数据，并且完善备份计划。