Oracle Backup and Recovery Issue
You should be able to just do a restore/recover over top of the existing Host2.  If you are trying to avoid a complete recovery, then I suspect the answer is you can't, but there are two notable exceptions.


If you never opened the database on Host2 and you have all the archive logs between the first backup and the second, then you can recover Host2 using them.  
If you have opened Host2, you still might be able to do this if you have flashback database enabled and can flash back to the point before you opened it.