Explanation:
A backup set and an image copy can be assigned as RMAN tag. RMAN allows the DBA to define a special name to be used in conjunction with an image copy or a backup set. This name is called a TAG. The tag may be up to 30 characters in length and has similar naming restrictions to other database objects. The tag can then be used in conjunction with restoring the backup set or image copy. Multiple backup objects can have the sametag. If a tag is specified for use in recovery, and more than one object corresponds to that tag, then the most recent object that is fit to use for the recovery will be the one RMAN uses.
Incorrect Answers:
1: A disk drive cannot be assigned as RMAN tag.
2: A tape drive cannot be assigned as RMAN tag.
4: A disk channel is used for different purposes and also cannot be assigned as RMAN tag.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 631-632
Chapter 13: Using Recovery Manager for backups

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