Re: Rollback segments minextents

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 16 Sep 1999 13:45:06 +0100
Message-ID: <937486451.8078.1.nnrp-13.9e984b29@news.demon.co.uk>

It dates back to a whitepaper written for Oracle 5 (though is still pretty relevant).

When a transaction cross an extent boundary no other transaction can begin in that extent.

Therefore in a 2-extent rbs, a single well (?badly?) placed transaction could make the entire rollback segment unusable for a period.

The more extents, the smaller the fraction of the segment that is unusable. 20 extents (all of the same size) denies ca. 10% of the RBS - the trade-off is between having
too many extents and losing too much
usable space in one shot.

Jonathan Lewis
Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk

Laurent La Fosse wrote in message <37E0DACD.66DF24F1_at_mediaone.net>...
>I would like to know why people recommend setting MINEXTENTS to 20
>when creating rollback segments?
Received on Thu Sep 16 1999 - 07:45:06 CDT