tablespaces in backup mode

I'm studying for a DBA exam using a book called "Oracle 8i Certified Professional DBA Practice Exams" by Jason Couchman. I came upon a question that confused me. It is

The DB A has just finished making operating system copies of datafiles for backup. Which of the folllowing choices identifies how the DBA should complete the backup?

1. Switch online redo logs, back up control file to trace, and take tablespaces out of backup mode
2. Back up control file to trace, switch online redo logs, save backup control file and redo logs to tape
3. Take binary copy of control file, take tablespaces out of backup mode, dismount database
4. Take tablespaces out of backup mode, back up control file to trace, switch online redo logs

The experts out there know that the answer is "D" and my question is, why do you take tablespaces out of backup mode first? Shouldn't that come at the end?

Thanks for any input anyone can provide, - Dave Received on Wed Mar 17 2004 - 11:18:05 CST