Re: Do I really need more than 1 rollback segment?

I've always said that there is plenty of scope of individual requirements taking systems far off the beaten track - but 800 rollback segments seems a bit extreme unless you are expecting in excess of about 4,000 concurrent transactions to be starting and stopping all the time.

However, the notes with this benchmark are really quite peculiar. I quote:

""""
For this 3TB benchmark, Oracle configured 650Gig of active log space and then mirrored these logs for a total disk usage of 1.3TB just for logs (rollback segments). 72 x 18.2GB drives. In contrast, the DB2 benchmark used only 23Gig of log space (30X less) for our 1TB TPC-H benchmark. Why did Oracle use so much log space?

Oracle claims that they have enhanced 9i with "automatic undo management" which is supposed to remove the burden of having to manage rollback segments. Decide for yourself if creating 800 rollback segments using 15 pages of create rollback statements removes the management burden. """"

Points to note

    With automatic undo management, you cannot create rollback segments,     so there would be no 15 pages of 'create rollback segment'.

    Given the apparent misconception regarding rollbacks, I have to ask whether

    the author of the phrase "1.3TB just for logs (rollback segments)" is sure that

    they are equating like with like when they compare Oracle's rollback segments

    with DB2's log space.

Of course, the whole thing is yet another of these 'little boys with big toys' slagging each other off in the playground. So it's clearly riddled with statements that are probably 100% true whilst being crafted to be as misleading as possible.

Unfortunately I wasted my time looking at it because I thought it was going to be an
interesting article.

--

Jonathan Lewis
http://www.jlcomp.demon.co.uk

Host to The Co-Operative Oracle Users' FAQ
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Author of:
Practical Oracle 8i: Building Efficient Databases

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Cyber Office wrote in message <9veteo$8061_at_imsp212.netvigator.com>...


>An interesting example of building a 3 TB Oracle database for TPC-H

>benchmark.  There are totally 800 rollback segments in the benchmark.