使用bbed修改文件头，推进scn，恢复offlinedrop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
http://blog.csdn.net/renfengjun/article/details/7944629
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。
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