Explanation:
If found corrupted redo log group is an inactive and not archived, you can use the ALTER DATABASE CLEAR UNARCHIVED LOGFILE GROUP 1 command to clear this redo log group. Issuing this statement will eliminate all redo information in the database redo log group specified. Only redo logs that have a status of inactive can be cleared. If the redo log being cleared has already been archived, then the DBA should not use the UNARCHIVED keyword. In the event that a redo log is found to be corrupt by the checksum process, the DBA must backup the database.
Incorrect Answers:
1: There is no RECOVER REDOLOG GROUP 1 command in Oracle.
2: This command should be used for cancel-based incomplete recovery.
3: There is no ALTER DATABASE RECOVER REDOLOG command in Oracle.
5: This command should be used for time-based incomplete recovery.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 662-663
Chapter 14: Database Failure and Recovery

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