Lost current Redo Log file

1. startup error message
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'D:\ORACLE\ORADATA\TEST\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) cannot find file
5.1.2 Current Redolog CorruptionTwo case:A. shutdown normally, no transaction to recovery, recreate log group with 'alter database clear unarchived logfile group n'B. active transaction exists. database need media recovery. log group need synchronized. there are 2 methods:a. imcomplete recovery. keep the consistence of database. but this method requires archivelog mode and valid backup.b. force recovery. but may cause inconsistence.
5.1.2.1 recovery with backup1. accounting a error when open database
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'D:\ORACLE\ORADATA\TEST\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2) OS cannot found file
2. check V$log, and notice the current redolog corrupted
SQL> select group#,sequence#,archived,status from v$log;

GROUP# SEQUENCE# ARCHIVED STATUS
---------- ---------- -------- ----------------
1 1 NO CURRENT
2 2 YES INACTIVE
3 3 YES INACTIVE
3. cannot clear the current redolog
SQL> alter database clear unarchived logfile group 1;
alter database clear unarchived logfile group 1
*
ERROR at line 1:
ORA-01624: log 1 needed for crash recovery of thread 1
ORA-00312: online log 1 thread 1: 'D:\ORACLE\ORADATA\TEST\REDO01.LOG'
4. copy a full backup and recover database
until scn or until cnacel
recover database until cancel
select auto recover with all the valid archivelogs and redologs, and
recover database until cancel
enter cancel to do a incomplete recovery (that's need recover twice)
Example:
SQL> recover database until cancel;
Auto
...
SQL> recover database until cancel;
Cancel;
5. open database with: alter database open resetlogsDescription:1. incomplete recovery may cause data lost of current redolog.2. need archivelog mode and full backup.3. backup database after recovery.4. strongly recomment that make log mirror on different disks.
5.1.2.2 force recovery without backup1. accounting a error
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: 'D:\ORACLE\ORADATA\TEST\REDO01.LOG'
ORA-27041: unable to open file
OSD-04002: unable to open file
O/S-Error: (OS 2)
2、notice curruent redolog corrupted
SQL> select group#,sequence#,archived,status from v$log;

GROUP# SEQUENCE# ARCHIVED STATUS
---------- ---------- -------- ----------------
1 1 NO CURRENT
2 2 YES INACTIVE
3 3 YES INACTIVE
3、cannot clear
SQL> alter database clear unarchived logfile group 1;
alter database clear unarchived logfile group 1
*
ERROR at line 1:
ORA-01624: log 1 needed for crash recovery of thread 1
ORA-00312: online log 1 thread 1: 'D:\ORACLE\ORADATA\TEST\REDO01.LOG'
4、shutdown database
SQL>shutdown immediate
5、add the following parameter to init.ora
_allow_resetlogs_corruption=TRUE
6、restart database and recover with 'until cancel'
SQL>recover database until cancel;
Cancel

SQL>alter database open resetlogs;
7、full export database after open database successfully
8、shutdown database, remove init parameter
_all_resetlogs_corrupt
9、recreate database
10、import and finish recovery
11、recomment to run
ANALYZE TABLE ...VALIDATE STRUCTURE CASCADE;
Description1. use this method only when no other method. because it may cause database inconsistent2. cause data loss, but less than recover with backup. because the data without commit be recovered too.3. strongly recomment run complete recreation and valication check.4. should backup database fullly.5. strongly recomment that make log mirror on different disks, no data loss can be accept on production environment.
Reference http://www.itpub.net/thread-126320-1-1.html