数据文件的三个创建SCN一点点探讨

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标题:数据文件的三个创建SCN一点点探讨

作者:惜分飞©版权所有[未经本人同意,不得以任何形式转载,否则有进一步追究法律责任的权利.]

在给一个朋友数据库恢复的过程中语句该库大量删除表空间,然后创建表空,由于在创建控制文件的时候,列出来不正确文件,导致出现v$datafile_header.error出现WRONG FILE CREATE错误.通过试验重现了该错误,并且进一步测试如果真的需要历史数据文件,该如何狸猫换太子(本实验为了进一步理解数据文件创建scn相关信息)
创建xifenfei表空间,然后删除表空间,但不删除数据文件,然后创建重名表空间

SQL> select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') today,'www.xifenfei.com' xifenfei from dual;

TODAY               XIFENFEI
------------------- ----------------
2014-07-16 15:54:26 www.xifenfei.com


SQL> create tablespace xifenfei datafile '/u01/app/oracle/oradata/ORCL/xifenfei_old.dbf' size 10m;

Tablespace created.

SQL> select file#,name from v$datafile;

     FILE# NAME
---------- --------------------------------------------------
         1 /u01/app/oracle/oradata/ORCL/system01.dbf
         2 /u01/app/oracle/oradata/ORCL/sysaux01.dbf
         3 /u01/app/oracle/oradata/ORCL/undotbs01.dbf
         4 /u01/app/oracle/oradata/ORCL/users01.dbf
         5 /u01/app/oracle/oradata/ORCL/xifenfei_old.dbf

SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593520 2014-07-16 16:00:54

SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile_header;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593520 2014-07-16 16:00:54

SQL> drop tablespace xifenfei;

Tablespace dropped.

SQL>  create tablespace xifenfei datafile '/u01/app/oracle/oradata/ORCL/xifenfei_new.dbf' size 10m;

Tablespace created.

SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593613 2014-07-16 16:02:45

SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile_header;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593613 2014-07-16 16:02:45

rename xifenfei表空间数据文件到老数据文件

SQL> alter database datafile 5 offline drop;

Database altered.

SQL> alter database rename file '/u01/app/oracle/oradata/ORCL/xifenfei_new.dbf'
 2   to '/u01/app/oracle/oradata/ORCL/xifenfei_old.dbf';     

Database altered.

SQL> alter database datafile 5 online;
alter database datafile 5 online
*
ERROR at line 1:
ORA-01122: database file 5 failed verification check
ORA-01110: data file 5: '/u01/app/oracle/oradata/ORCL/xifenfei_old.dbf'
ORA-01203: wrong incarnation of this file - wrong creation SCN


SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593613 2014-07-16 16:02:45

SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile_header;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593520 2014-07-16 16:00:54

SQL> select file#,error from v$datafile_header;

     FILE# ERROR
---------- -----------------------------------------------------------------
         1
         2
         3
         4
         5 WRONG FILE CREATE

至此今天数据库恢复的故障已经模拟出来,就是因为数据文件头的scn和控制文件中scn不一致,从而出现了v$datafile_header.error报WRONG FILE CREATE的现象.

因为控制文件中数据文件scn和数据文件头scn不一致,因此通过重建控制文件来实现两者scn一致

SQL> alter database backup controlfile to trace as '/tmp/ctl';

Database altered.

SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> STARTUP NOMOUNT
ORACLE instance started.

Total System Global Area  718225408 bytes
Fixed Size                  2292432 bytes
Variable Size             373294384 bytes
Database Buffers          339738624 bytes
Redo Buffers                2899968 bytes
SQL> CREATE CONTROLFILE REUSE DATABASE "ORCL" NORESETLOGS  NOARCHIVELOG
  2      MAXLOGFILES 16
  3      MAXLOGMEMBERS 3
  4      MAXDATAFILES 100
  5      MAXINSTANCES 8
  6      MAXLOGHISTORY 292
  7  LOGFILE
  8    GROUP 1 '/u01/app/oracle/oradata/ORCL/redo01.log'  SIZE 50M BLOCKSIZE 512,
  9    GROUP 2 '/u01/app/oracle/oradata/ORCL/redo02.log'  SIZE 50M BLOCKSIZE 512,
 10    GROUP 3 '/u01/app/oracle/oradata/ORCL/redo03.log'  SIZE 50M BLOCKSIZE 512
 11  DATAFILE
 12    '/u01/app/oracle/oradata/ORCL/system01.dbf',
 13    '/u01/app/oracle/oradata/ORCL/sysaux01.dbf',
 14    '/u01/app/oracle/oradata/ORCL/undotbs01.dbf',
 15    '/u01/app/oracle/oradata/ORCL/users01.dbf',
 16    '/u01/app/oracle/oradata/ORCL/xifenfei_old.dbf'
 17  CHARACTER SET ZHS16GBK
 18  ;

Control file created.

SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile_header;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593520 2014-07-16 16:00:54

SQL> select file#,CREATION_CHANGE#,to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATION_TIME from v$datafile;

     FILE# CREATION_CHANGE# CREATION_TIME
---------- ---------------- -------------------
         1               18 2014-07-14 21:53:05
         2             2338 2014-07-14 21:53:42
         3             3130 2014-07-14 21:53:51
         4            15268 2014-07-14 21:54:25
         5           593520 2014-07-16 16:00:54

SQL> select file#,error from v$datafile_header;

     FILE# ERROR
---------- -----------------------------------------------------------------
         1
         2
         3
         4
         5

通过重建控制文件消除了v$datafile_header.error报WRONG FILE CREATE错误,继续尝试online文件

SQL> recover datafile 5;
Media recovery complete.
SQL> alter database datafile 5 online;

Database altered.

SQL> select file#,name from v$datafile;

     FILE# NAME
---------- --------------------------------------------------
         1 /u01/app/oracle/oradata/ORCL/system01.dbf
         2 /u01/app/oracle/oradata/ORCL/sysaux01.dbf
         3 /u01/app/oracle/oradata/ORCL/undotbs01.dbf
         4 /u01/app/oracle/oradata/ORCL/users01.dbf
         5 /u01/app/oracle/oradata/ORCL/xifenfei_old.dbf

SQL> alter database open;
ORA-01092: ORACLE instance terminated. Disconnection forced
ORA-01177: data file does not match dictionary - probably old incarnation
ORA-01110: data file 5: '/u01/app/oracle/oradata/ORCL/xifenfei_old.dbf'
Process ID: 7437
Session ID: 7 Serial number: 5

出现这个错误,是由于数据库中,还有file$中也记录了数据文件创建scn,而这个scn现在和数据文件头和控制文件中的scn不相等,因此无法启动数据库成功.现在需要做的就是在数据库未启动状态下修改file$中的数据文件创建scn相关值,让其和数据文件头(控制文件中记录)一致

使用第三方工具定位file$记录

1|2|89600|0|1|4194302|1280|0|18||4194306|0x004000e9|0
2|2|70400|1|2|4194302|1280|0|2338||8388610|0x004000e9|1
3|2|25600|2|3|4194302|640|0|3130||12582914|0x004000e9|2
4|2|640|4|4|4194302|160|0|15268||16777218|0x004000e9|3
5|2|1280|7|5|0|0|0|593613||20971522|0x004000e9|4   
6|1|3840|||0|0|0|586295||25165826|0x004000e9|5
7|1|3840|||3932160|1280|0|587030||29360130|0x004000e9|6
对应file$结构确定每列含义,以及确定需要修改的列
每行倒数第二列为rdba地址,可以通过转换为file and block,这里对应的就是file 1 block 233
每行最后一列为该条记录在该rdba中的记录顺序

使用工具修改593613为593520,使得file$中的scn与现在控制文件和数据文件头一致,具体参考bbed修改数据内容

修改好file$中数据文件创建scn后,尝试继续操作

SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01113: file 5 needs media recovery
ORA-01110: data file 5: '/u01/app/oracle/oradata/ORCL/xifenfei_old.dbf'

SQL> recover datafile 5;
Media recovery complete.
SQL> alter database open;

Database altered.

SQL> select file#,name from v$datafile;

     FILE# NAME
---------- --------------------------------------------------
         1 /u01/app/oracle/oradata/ORCL/system01.dbf
         2 /u01/app/oracle/oradata/ORCL/sysaux01.dbf
         3 /u01/app/oracle/oradata/ORCL/undotbs01.dbf
         4 /u01/app/oracle/oradata/ORCL/users01.dbf
         5 /u01/app/oracle/oradata/ORCL/xifenfei_old.dbf

通过这里的简单测试,发现几个问题
1.v$datafile_header.error报WRONG FILE CREATE错误 不一定就是数据文件异常,而其本质是数据文件头scn和控制文件中scn不一致
2.数据文件online需要file$,v$datafile_header,v$datafile中关于数据文件创建scn都一致
3.通过该分析,证明在一些极端情况下,考虑考虑该替换思路实现删除数据文件重新加入数据库

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