linux重装后文件会不会丢失,重做日志文件丢失的恢复(二)

丢失的日志文件的状态如果是ACTIVE或CURRENT，说明没有归档。如果没有归档的日志组中含有多个日志文件成员，那么丢失或者损坏部分日志文件时，只需要复制正常的日志文件，来替换丢失或损坏的日志文件即可解决，这样数据不会丢失，也不用做恢复操作。

如果没有归档的重做日志组中所有日志件都丢失或者损坏，将会导致数据库数据丢失，如果没有归档的日志文件组为当前组，则数据库立即DOWN机。当这个情况发生时，就意味着数据的丢失，我们只能将数据库恢复到前一次的归档日志切换时刻

下面模拟在正常和非正常关闭数据库后丢失当前日志文件的场景，来恢复日志文件。

因为是正常关闭，因此数据库在关闭前，做了全面检查点，日志文件对实例恢复没有意义了。

测试环境

SQL> select * from v$version;

BANNER

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

Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production

PL/SQL Release 11.1.0.6.0 - Production

CORE11.1.0.6.0Production

TNS for Linux: Version 11.1.0.6.0 - Production

NLSRTL Version 11.1.0.6.0 – Production

SQL> select group#,members,status from v$log;

GROUP#MEMBERS STATUS

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

12 INACTIVE

21 CURRENT

32 INACTIVE

模拟丢失文件

SQL> shutdown immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> !rm /u01/oradata1/redo02.log

SQL> startup

ORACLE instance started.

Total System Global Area146472960 bytes

Fixed Size1298472 bytes

Variable Size92278744 bytes

Database Buffers50331648 bytes

Redo Buffers2564096 bytes

Database mounted.

ORA-00313: open failed for members of log group 2 of thread 1

ORA-00312: online log 2 thread 1: '/u01/oradata1/redo02.log'

SQL> !ls -l /u01/oradata1

total 102528

-rw-r-----1 oracle oinstall 52429312 Sep 26 03:49 redo010.log

进行恢复

SQL> alter database clear unarchived logfile group 2;

Database altered.

检查发现，日志文件已恢复。

SQL> !ls -l /u01/oradata1

total 102528

-rw-r-----1 oracle oinstall 52429312 Sep 26 03:49 redo010.log

-rw-r-----1 oracle oinstall 52429312 Sep 26 03:54 redo02.log

SQL> alter database open;

Database altered.

，丢失当前日志文件的恢复

异常关闭数据库，说明在数据库启动时进行的实例恢复一定要求有当前的日志文件，否则oracle将无法保证提交的成功的数据部丢失。

测试环境

SQL> select * from v$version;

BANNER

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

Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production

PL/SQL Release 11.1.0.6.0 - Production

CORE11.1.0.6.0Production

TNS for Linux: Version 11.1.0.6.0 - Production

NLSRTL Version 11.1.0.6.0 – Production

SQL> select group#,members,status from v$log;

GROUP#MEMBERS STATUS

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

12 INACTIVE

21 CURRENT

32 INACTIVE

模拟丢失文件

SQL> shutdown abort

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> !rm /u01/oradata1/redo02.log

SQL> startup

ORACLE instance started.

Total System Global Area146472960 bytes

Fixed Size1298472 bytes

Variable Size92278744 bytes

Database Buffers50331648 bytes

Redo Buffers2564096 bytes

Database mounted.

ORA-00313: open failed for members of log group 2 of thread 1

ORA-00312: online log 2 thread 1: '/u01/oradata1/redo02.log'

SQL> !ls -l /u01/oradata1

total 102528

-rw-r-----1 oracle oinstall 52429312 Sep 26 03:49 redo010.log

进行恢复

该参数默认值为FALSE，为TRUE说明，在破坏唯一性的情况下强制重置日志，打开数据库。在打开的过程中，ORACLE会跳过一致性检查，使数据库处于不一致的状态下打开。

SQL> alter system set "_allow_resetlogs_corruption"=true scope=spfile;

System altered.

修改后，重启数据库。

SQL> shutdown immeditae

ORA-01109: database not open

Database dismounted.

ORACLE instance shut down.

SQL> startup mount

ORACLE instance started.

Total System Global Area146472960 bytes

Fixed Size1298472 bytes

Variable Size92278744 bytes

Database Buffers50331648 bytes

Redo Buffers2564096 bytes

Database mounted.

SQL> recover database using backup controlfile until cancel;

ORA-00279: change 3046568 generated at 09/26/2010 00:59:56 needed for thread 1

ORA-00289: suggestion :

/u01/flash_recovery_area/ORCL/archivelog/2010_09_26/o1_mf_1_2_%u_.arc

ORA-00280: change 3046568 for thread 1 is in sequence #2

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

cancel

ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below

ORA-01194: file 1 needs more recovery to be consistent

ORA-01110: data file 1: '/u01/oradata/orcl/system01.dbf'

ORA-01112: media recovery not started

如果这里出现错误，跳过即可

SQL> alter database open resetlogs;

Database altered.

检查发现，日志文件已恢复。

SQL> !ls -l /u01/oradata1

total 102528

-rw-r-----1 oracle oinstall 52429312 Sep 26 03:49 redo010.log

-rw-r-----1 oracle oinstall 52429312 Sep 26 03:54 redo02.log

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORACLE instance started.

Total System Global Area146472960 bytes

Fixed Size1298472 bytes

Variable Size92278744 bytes

Database Buffers50331648 bytes

Redo Buffers2564096 bytes

Database mounted.

Database opened.

数据库被打开后，马上执行全备，shutdown数据库,修改_all_resetlogs_corrupt参数为FALSE.