I have a DB running in archivelog mode with 2GB of archive logs. This DB has never been backed up by the RMAN catalog I just set up. I wonder when I do RMAN whole DB inconsistent/hot backup for the very first time, I can use BACKUP DATABASE PLUS ARCHIVELOG, what archived logs are backed up? I suppose it backs up ALL the archived logs it can find because this is the first time it backs them up? However, is it really necessary to back up ALL the 2GB archived logs along with the DB files, etc.? Chances are most of the older archived log will not be used even if I have to do a recovery from this whole DB backup. Am I correct?
I suppose when dealing with this kind of situation, it's better to mount the target db and do a cold rman backup first?
Since you don't have a baseline backup, most of the old archived redo logs are useless. The first thing you should do with your first backup is archive the current log file. Then start backing up your database. You will generate redo during your backup, so you will want to backup this redo so you can restore a consistent database. After that, backup all your archived redo logs every day.