Explanation:
When the status of the table space changes from read-only to read-write, there are two events occur: redo log switch must tale place and normal checkpoints on the file now occur, because for read-only table space there is no need for redo log changes and checkpoints. When database data is defined as read-only, the DBA needs to back up the read-only table space once, after the status of the table space is changed to readonly.
Incorrect Answers:
3: Oracle automatically does not mean the file for backup, it's DBA's responsibility to backup datafiles of table space, when it became read-write.
4: There is no object integrity check after table space status change.
5: The DBWn process writes to the data files of the table space only if it will be changes in data of table space, not because of table space status change.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 593
Chapter 12: Overview of Backup and Recovery

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