Hi,
when you switch a tablespace in HotBackup-Mode Oracle not only writes Block-changes to the log, but even whole modified ORacle-Blocks;
Why?
If your Oracle-block would greater than yours OS-Block it coild be happen that your backup-tool reads for example the half Oracle-block, when it tires to rad the next then it ( the Oracle-block ) could be changed. You have backuped an inconsistent Oracle-Block.
Due to HotBackup-Mode Oracle can complete tht Blocks data totally due to the block-wise logging.

The best Method to backup is with rman :

* No HotBackup-Mode
* Smaller Backup-files
* Blockconsitsency-check while backing up
* incremental Backups
* intelligent support due to repository when you recover the db

Orca