今天在公司帮开发部门打开一个测试库，到open状态时，报以下错误：

SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01122: database file 6failed verification check
ORA-01110: data file 6: '/u02/oradata/crmdb/test01.dbf'
ORA-01251: Unknown File Header Version read for file number 6

提示数据文件6的文件头信息已经损坏，不能正确读取

分三种情况恢复：

第一.非归档模式 则会丢失这个表空间下的所有数据

fix:

Drop the datafile and the associated tablespace.
1. Connect to the database as a user with SYSDBA privileges.
SVRMGRL>connect sys/ as SYSDBA;
2. Mount the database.
SVRMGRL>startup mount;
3. Drop the datafile specified in the error message.
SVRGMRL>alter database datafile '' offline drop;
4. Open the database.
SVRMGRL>alter database open;
5. Drop the tablespace associated with the datafile.
SVRMGRL>drop tablespace '' including contents;

第二.归档模式，并且创建这个数据文件以来的归档日志都在

1. The database needs to be in Archive log mode.
2. You need to have all the Archive log file from the time the datafile was created .
3. The control file should have datafile created information.If the controlfile was re-created
    after the datafile was created then the below solution will not work and step 2 will
    error with ORA-01178

Steps to be followed
====================

Step1 :-

Take the problematic datafile offline.

SQL> Alter database datafile  '/oracle/test_lob12.dbf' offline;

Copy the file to an alternate backup location.

Step 2:-

Issue the following command to re-create the file :

SQL> Alter database create datafile   '/oracle/test_lob12.dbf';

Step 3:-

Start applying the archive log file to recreate datafile.

SQL> Recover  datafile  '/oracle/test_lob12.dbf';

Step 4:-

When the recovery is finished, bring the datafile online.

SQL> Alter database datafile '/oracle/test_lob12.dbf' online;

3.用dul工具直接提取数据文件中的数据

    这个提取数据难度就有点高。