Explanation:
You need to use initialization parameter to specify whether archiving will be manual or automatic when configuring a database for ARCHIVE LOG mode.
Incorrect Answers:
1: The size of archived log files is not set with initialization parameters: all files have the same size as online redo log files.
2: Redo log file will be archived as soon as it became not current and you can control only frequency of redo log files checkpoints, not frequency of archiving itself.
3: The database is already set to ARCHIVE LOG mode by definition.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 577-583
Chapter 12: Overview of Backup and Recovery

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