Oracle Hot Backup Theory After a hot backup, where all tablespaces are placed in backup mode seperately; i.e.

alter tablespace user_data start backup;


each datafile will have a different Checkpoint SCN in its header; with the equivalent redo log files which will bring it up to date.

Why doesn't this non-sync of Checkpoint SCN cause a problem when restoring and recovering these datafiles?  The "checkpoint" SCN of each datafile is different from other datafiles and probably different from the control file's recorded SCN as well; doesn't this cause a problem?

Addition

Doesn't the inconsistency of the SCN in the datafiles cause a problem when SMON checks them once we decide to restore and recover the database using the hot backup?
When in doubt ask Tom...

backup up and recovery generating extra redo
Which is good reason to use RMAN for backups rather than 
scripted hot backups using begin backup/end backup.