使用alter database datafile 'XXX' offline drop 是否能够恢复(非归档模式下)

今天在群里面听到一位网友在说使用了alter database datafile 'XXX' offline drop命令是否能够恢复数据，在非归档模式下，下面是用一个实验来验证一下

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SQL> create tablespace test datafile '/u01/app/oracle/oradata/orcl/test01.dbf' size 10M autoextend on next 1M;

 

Tablespace created.

 

SQL> create table test(id number,name varchar2(12)) tablespace test;                                              

Table created.

 

SQL> insert into test values (1,'colin');

 

1 row created.

 

SQL> insert into test values (2,'janey');

 

1 row created.

 

SQL> insert into test values (3,'tom');

 

1 row created.

 

SQL> insert into test values (4,'adele');

 

1 row created.

 

SQL> commit;

 

Commit complete.

 

SQL> select * from test;

 

        ID NAME

---------- ------------

         1 colin

         2 janey

         3 tom

         4 adele

 

SQL> alter database datafile '/u01/app/oracle/oradata/orcl/test01.dbf' offline drop;

 

Database altered.

 

SQL> commit;

 

Commit complete.

 

SQL> select * from test;

select * from test

              *

ERROR at line 1:

ORA-00376: file 2 cannot be read at this time

ORA-01110: data file 2: '/u01/app/oracle/oradata/orcl/test01.dbf'

 

SQL> select LOG_MODE,OPEN_MODE from v$database;

 

LOG_MODE     OPEN_MODE

------------ ----------

NOARCHIVELOG READ WRITE

 

SQL> alter database datafile '/u01/app/oracle/oradata/orcl/test01.dbf' online;

alter database datafile '/u01/app/oracle/oradata/orcl/test01.dbf' online

*

ERROR at line 1:

ORA-01113: file 2 needs media recovery

ORA-01110: data file 2: '/u01/app/oracle/oradata/orcl/test01.dbf'

 

SQL> recover datafile '/u01/app/oracle/oradata/orcl/test01.dbf';

Media recovery complete.

SQL> alter database datafile '/u01/app/oracle/oradata/orcl/test01.dbf' online;

 

Database altered.

 

SQL> select * from test;

 

        ID NAME

---------- ------------

         1 colin

         2 janey

         3 tom

         4 adele

 

恢复成功。那是因为日志还没有切换，使用了online日志。

 

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切换日志来测试：

 

SQL> alter database datafile '/u01/app/oracle/oradata/orcl/test01.dbf' offline drop;

 

Database altered.

 

SQL> select * from test;

select * from test

*

ERROR at line 1:

ORA-00376: file 2 cannot be read at this time

ORA-01110: data file 2: '/u01/app/oracle/oradata/orcl/test01.dbf'

 

SQL> alter system switch logfile;

 

System altered.

 

SQL> /

 

System altered.

 

SQL> /

/

 

System altered.

 

SQL> 

System altered.

 

SQL> recover datafile '/u01/app/oracle/oradata/orcl/test01.dbf';

ORA-00279: change 654004 generated at 07/09/2012 21:07:18 needed for thread 1

ORA-00289: suggestion : /u01/app/oracle/arch/1_32_777559117.arc

ORA-00280: change 654004 for thread 1 is in sequence #32

 

Specify log: {=suggested | filename | AUTO | CANCEL}

cancel

Media recovery cancelled.

SQL> /

 

System altered.

 

SQL> recover datafile '/u01/app/oracle/oradata/orcl/test01.dbf';

ORA-00279: change 654004 generated at 07/09/2012 21:07:18 needed for thread 1

ORA-00289: suggestion : /u01/app/oracle/arch/1_32_777559117.arc

ORA-00280: change 654004 for thread 1 is in sequence #32

 

Specify log: {=suggested | filename | AUTO | CANCEL}

auto

ORA-00308: cannot open archived log '/u01/app/oracle/arch/1_32_777559117.arc'

ORA-27037: unable to obtain file status

Linux Error: 2: No such file or directory

Additional information: 3

 

ORA-00308: cannot open archived log '/u01/app/oracle/arch/1_32_777559117.arc'

ORA-27037: unable to obtain file status

Linux Error: 2: No such file or directory

Additional information: 3

 

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通过以上测试表明，在非归档模式下使用了alter database datafile 'XXX' offline drop命令是不能被恢复的，虽然我上面的第一次实验成功了，那是因为online日志还没有切换，在日志中还能够找到相应的反操作。在第二个实验中，手工切换日志，会提示不能打开归档日志，因为我根本就没有归档，肯定找不到啊，所以不能够恢复的。切记，在非归档模型下不要随意使用一些drop命令，在实际生产环境中日志的切换是很频繁且快的，否则只有掏钱找oracle了。当然，如果在业务不繁忙的系统可以及时的通过online日志进行恢复，这种几率比较小。

 

文章：http://blog.csdn.net/colin_liu2009/article/details/7736965