Re: IBM Debunks Oracle's MultiVersion Read Consistency ?

Galen Boyer wrote:

> On Sun, 20 Apr 2003, rallen_at_NOSPAMOKhgi.com wrote:
>
> > They raise some good points. Is it really as efficient as IBM
> > suggests? What are the advantages that MVRC provide?
>
> The thing that struck me as silly is that they crow about supporting
> ReadUncommitted. Why is this ever a good thing (except when you might
> be blocking and need some way to move one, ala SQLServer and it sounds
> like DB2) If you read any uncommitted data and then after you've read it
> the writer of that data rollsback, then what good was the read?
>
> I like the fact that Oracle says, whatever is committed is boss, period.
>
> Others?
>
> Even committed transactions are not seen by the reader if the reading
> statement started before the updating statement.
>
> I think Oracle chose the correct way to go. If a row you already read
> gets updated before you are done with your full read, what should your
> answer contain?
>
> To get around this well known Oracle problem, application developers
> will write their applications and commit as infrequently as
> possible.
>
> Eh? Oracle allows us to commit when the business logic says so, period.
>
> Oracle's concurrency model is page based.
>
> So. The problem there is they try to say that both transactions can't
> proceed when they are blocking different rows on the same page. All
> this says to me is that Oracle only writes out pages, therefore it will
> have multiple versions of the same pages based on the concurrency
> needs. Lumping it together to try and imply Oracle's transactions block
> readers is just devious.
>
> --
> Galen deForest Boyer
> Sweet dreams and flying machines in pieces on the ground.

I don't like to engage in meaningless product bashing ... so I won't. But if you want a chuckle ... take a look at this web site: http://www.db2seattle.org/

I will engage in no editorializing ... no doubt you will come to the same realizations without any help.

--
Daniel Morgan
http://www.outreach.washington.edu/extinfo/certprog/oad/oad_crs.asp
(remove one 'x' from my email address to reply)