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Steps to recreate an Inactive Online Redo Log

To recreate an inactive online redo log manually, do the following:
  1. Find a location to recreate the online redo log.
  2. Drop the damaged or lost log file.
  3. Add the log group.
  4. Open the database and do not forget to multiplex all redo logs to reduce the chance of losing data.

Recovering from Loss of Multiplexed Redo Log File

When one of the multiplexed members of any group is corrupted or accidently dropped, the LGWR process ignores it and writes the information to the only available member. The following scenario gives a demonstration to easily understand the main concept:

SQL>  
select
 b.group#, a.status, b.status, b.member 
 from
  v$log a, v$logfile b 
  where
   a.group#=b.group#
   order by
   1,2;
Add one member to each redo log group. Query all redo log members and their status:

GROUP# STATUS         MEMBER
 ----  ------------  --------------------------------
1 			CURRENT        /u01/oracle/product/10.2.0/db_1/ora
                      data/testdb/redo01.log
2 			INACTIVE       /u01/oracle/product/10.2.0/db_1/ora
                      data/testdb/redo02.log
3 			ACTIVE         /u01/oracle/product/10.2.0/db_1/ora
                      data/testdb/redo03.log