From: <>
Date: Thu, 28 Aug 2008 06:46:56 +0200
Message-ID: <>

On Wed, 27 Aug 2008 13:13:46 -0700 (PDT), wrote:

>Forgive me for this last question.
>I think I understand backupset & backuppiece. Usually each backupset
>is allocated to a different channel.
>Filesperset I'll have to do a bit more reading on as to understand why
>3 files writing to 3 different backup sets vs 3 files writing to 1
>backup set makes a difference.
>MAXSETSIZE sets the maximum size per backupset, I assume. Would
>setting both filesperset & maxsizeset conflict? I'm trying to think
>about this. If you have 12 files, and you say you want 4 files per
>set, thus 3 sets, and a maxsize of 50G per may get more
>than 3 sets, defined by the previous filesperset value......
>I'm probably wrong.....

backupsets are NOT allocated to different channels unless you instruct it do so. Channels are backup destinations, sending subsequent backupsets to different channels doesn't make sense.

Three files written to 1 backupset are three files opened *simultaneously* (by three different Oracle sessions), read in parallel, and written in parallel to 1 backupset.

Rman will calculate the space required, with as guideline a datafile can't span a backupset. If 4 files don't fit in 50 G, RMAN will create extra sets and adjust the number of filesperset automatically.

Sybrand Bakker
Senior Oracle DBA
Received on Wed Aug 27 2008 - 23:46:56 CDT

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