Re: Space wasted because of automatic undo management

From: Matthias Hoys <idmwarpzone_NOSPAM__at_yahoo.com>
Date: Fri, 1 Apr 2005 20:39:11 +0200
Message-ID: <424d9550$0$30478$ba620e4c@news.skynet.be>

"Vsevolod Afanassiev" <vafanassiev_at_yahoo.com> wrote in message news:1112321274.554117.136870_at_f14g2000cwb.googlegroups.com...
> Let's say I am using traditional rollback segments. For a small
> database I would create 4 segments, each 100 MB in size, and set
> OPTIMAL to 100 MB. All 4 segments will be in the same tablespace and in
> the same datafile, so initial datafile size will be 400 MB.
> It may grow if there is a large transaction, but eventually the
> transaction will complete, rollback segment shrink back to OPTIMAL
> size, and the datafile could be resized back to 400 MB. So the space is
> used efficiently and not wasted.
>

"It may grow if there is a large transaction" : true !! But this also means that you need this diskspace to be ALWAYS available, right ? This means that the allocated space for the rollback segments is not "wasted", it's just "on hold" until a large transaction needs it. Same with diskspace needed for the TEMP tablespace. The diskspace needed for rollback depends on your largest transactions, and not vice-versa.

Matthias Received on Fri Apr 01 2005 - 12:39:11 CST