Which of the following statements is true when the database is in ARCHIVELOG mode and
tablespaces are in hot backup mode?
A. Archive log generation is suspended until the tablespaces are taken out of hot backup mode.
B. Datafiles are not written to during hot backups.
C. Changes to the database are cached during the backup and not written to the datafiles to ensure that
the datafiles are consistent when recovered.
D. The datafile headers are not updated during the backup.
E. The way data is written to the online redo logs is unchanged during the backup.
When you issue the alter database backup mode,the related datafile headers are not
updated. The headers will be update after the tablespaces are taken out of hot backup mode.
原文：http://www.cnblogs.com/Babylon/p/7792663.html