Explanation:
Oracle performs a delayed block clean out and flushes the dirty blocks in he database buffer cache to disk during a checkpoint. A checkpoint is when Oracle writes all dirty buffers in the buffer cache to disk. Behind the scenes, Oracle's CKRT process marks the datafile header as current, and records the sequence number for the current checkpoint in the control file(s). Checkpoints are used to ensure that, at some point, all of the information in both the buffer cache is copied to disk, which synchronizes write activities performed by LGWR and DBWR.
Incorrect Answers:
1: A checkpoint will occur at least as often as a log switch, but can occur more frequently, depending on several factors.
2: Oracle does not perform a control file. Control file is used to mount and open database.
4: Oracle copies the online redo log files to the archive destinations regardless a checkpoint.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 5695-571
Chapter 12: Overview of Backup and Recovery

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