Explanation:
There is no need to take an operation system backup of the database files for the open database backup.
Incorrect Answers:
1: For hot backup the database must be actually in ARCHIVELOG mode.
2: The database is available for use during hot backups without restrictions.
3: All the datafiles copied during hot backup are consistent to a point-in-time by definition of hot backup.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 587-590
Chapter 12: Overview of Backup and Recovery

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