If you have lost an online redo log file, then you can recreate it by opening the database with the RESETLOGS option. You can perform the following steps:
CONNECT / AS SYSDBA
ALTER DATABASE OPEN RESETLOGS;
Your missing online redo logs will be recreated. Since you performed a RESETLOGS operation, it is a very good idea to take a backup of your database immediately.
This was first published in March 2005