How can I recover the Oracle 9i database when I lost the current online redo log group in a 24x7 environment?

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If you lose the current online redo log, then you will not be able to recover the information in that online redo log. This is one reason why redo logs should be multiplexed. If it is multiplexed, you will have a copy of the online redo log. Let's assume that your online redo log group #1 has two members, redo01a.log and redo01b.log. If redo01a.log is missing, simply shutdown the database and copy redo01b.log and rename it to redo01a.log. You should be able to start the database.

If you have not multiplexed your online redo logs, then you are only left with incomplete recovery. Your steps are as follows:

  1. SHUTDOWN ABORT
  2. STARTUP MOUNT
  3. RECOVER DATABASE UNTIL CANCEL;
  4. When you have applied any archived redo logs, then reply CANCEL to stop the recovery process.
  5. ALTER DATABASE OPEN RESETLOGS;
The last step will recreate your missing log files. Any transactions in those missing log files that were not written to disk are now lost. Any time you open with RESETLOGS, make sure you shutdown the database and take a good backup.

This was first published in July 2004

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