Oracle联机日志文件记录数据库运行过程中数据块改变的日志，在数据库出现介质损坏或者异常挂掉后，需要通过联机日志（或归档）日志，重演数据库发生的改变。
在日志文件本身出现损坏（丢失）的情况下，数据库可能出现无法正常打开，本文就是针对这种情况下进行的恢复测试（仅供参考）：
Oracle调整联机重做日志大小(change redo log size)
Oracle 联机重做日志文件(ONLINE LOG FILE)
Oracle 联机重做日志文件(online redo log file) 详述
一、日志文件损坏分类：
1、inactive 状态（不会造成数据丢失）
2、active、current状态（一般会造成数据丢失）
查看方法：
SQL> select group#,thread#,archived,status from v$log;
GROUP# THREAD# ARC STATUS
---------- ---------- --- ----------------
1 1 YES INACTIVE
2 1 NO CURRENT
3 1 YES INACTIVE
二、测试环境：
•OS: Linux xxxxxxxx 2.6.18-238.el5 #1 SMP Thu Jan 13 15:51:15 EST 2011 x86_64 x86_64 x86_64 GNU/Linux
•DB: oracle 11.2.0.1.6（非RAC)
三、inactive 状态日志文件损坏的恢复测试：
startup时错误日志：
SQL> startup
ORACLE instance started.
Total System Global Area 3156877312 bytes
Fixed Size 2217424 bytes
Variable Size 989858352 bytes
Database Buffers 2147483648 bytes
Redo Buffers 17317888 bytes
Database mounted.
ORA-03113: end-of-file on communication channel
Process ID: 29499
Session ID: 2273 Serial number: 5
alert错误日志：
Errors in file /u01/oracle/diag/rdbms/test/test/trace/test_lgwr_29457.trc:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: '/u01/test/test/redo01.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
Errors in file /u01/oracle/diag/rdbms/test/test/trace/test_lgwr_29457.trc:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: '/u01/test/test/redo01.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
Errors in file /u01/oracle/diag/rdbms/test/test/trace/test_ora_29499.trc:
ORA-00313: open failed for members of log group 1 of thread
ORA-00312: online log 1 thread 1: '/u01/test/test/redo01.log'
USER (ospid: 29499): terminating the instance due to error 313
Instance terminated by USER, pid = 29499
这种情况下，只需将active的日志组删除，然后startup，如下：
SQL> startup mount;
ORACLE instance started.
Total System Global Area 3156877312 bytes
Fixed Size 2217424 bytes
Variable Size 989858352 bytes
Database Buffers 2147483648 bytes
Redo Buffers 17317888 bytes
Database mounted.
SQL> alter database drop logfile group 1;
Database altered.
SQL> alter database open;
Database altered.
四、active、current日志文件损坏：
startup时错误：
SQL> startup
ORACLE instance started.
Total System Global Area 3156877312 bytes
Fixed Size 2217424 bytes
Variable Size 989858352 bytes
Database Buffers 2147483648 bytes
Redo Buffers 17317888 bytes
Database mounted.
ORA-00313: open failed for members of log group 3 of thread 1
ORA-00312: online log 3 thread 1: '/u01/test/test/redo03.log'
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
SQL> select group#,thread#,archived,status from v$log;
GROUP# THREAD# ARC STATUS
---------- ---------- --- ----------------
1 1 NO CURRENT
3 1 YES ACTIVE
2 1 YES INACTIVE