Re: Trying to understand RMAN's backup-sets

José Arango wrote:
> Hello everyone,
>
> I'm learning about RMAN. I did a couple of backups on my test database. This
> database has over 300 data files (~14GB). The backup ends with 4 backup
> sets (each one having a backup piece). When I do "list backup" (this is
> 8.1.7 RMAN) I see the 4 backup sets:
>
> backup set 1
> ------- one backup piece
> -------------------the piece includes: like 80 datafiles...
>
> backup set 2
> -------- one backup piece
> -------------------the piece includes: like 80 datafiles..
>
> and so on...
>
> My problem is: I thought that a "backup set" was the term you use when you
> perform a backup and that when you perform a backup...that's just one
> "backup set" (with one or more backup pieces). Why am I getting 4 backup
> sets? Shouldn't I have 1 backup set with 4 backup pieces (and all datafiles
> within those 4 pieces)? If I do another backup tomorrow, that's Monday
> bakcup-set...etc... What is it that I'm missing?
>
> Thanks in advance!
> Jose
>

Frankly, it doesn't really matter.

But no, issuing one "backup" command can result in multiple backup sets, because of the number of channels (each channel outputs its own backup set, for example). And FILESPERSET also means that you can cause a single backup of a database to be broken up into separate backupsets.

The business of pieces really comes about only because of file size limitations with your file system or because of a MAXPIECESIZE setting. So, one channel busy outputting 10 files, say, hits the 2GB file size limit, and therefore has to start outputting another 2GB piece.

I gave up worrying about what a piece was as opposed to a set a long time ago. I can't think that it has ever made a difference to how I back up or what I type when I recover.

Regards
HJR Received on Mon Nov 15 2004 - 02:04:42 CST