Explanation:
RMAN enables you to open the target database using the OPEN DATABASE command. To mount the target database from NOMOUNT state, you must execute the MOUNT DATABASE command. Alternatively, you can also use the ALTER DATABASE MOUNT and ALTER DATABASE OPEN commands.
Reference:
Oracle 9i Net Services Administrator’s Guide
Oracle 9i Net Services Reference Guide
Oracle 9i Recovery Manager Reference
Oracle 9i Backup and Recovery Concepts

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