Re: Re: 24 x 7 x 365

Jonathan,
Thanks for this valuable information.
However, I'm using regular commits, not "distributed" two-phased ones and I just have simple code to handle the situation where servers return different success/error codes.

Tanel.

>
> There is a problem with this approach
> that may only become apparent at high
> concurrency.
>
> Since you are operating with two-phase
> commits, you may come up against the case
> where "writers block readers".
>
> Your client issues a commit to both servers.
> Each server get the PREPARE message,
> and when both have responded, each gets
> the COMMIT message.
>
> Between the PREPARE and COMMIT,
> any blocks updated in the transaction
> cease to be available to ANY query
> that started after the PREPARE arrived.
>
> For the (hopefully) brief interval between
> the prepare and commit, neither database
> knows whether the transaction as a whole
> has prepared or committed, so any process
> that wants to see the current version of the
> data has to wait until there is a known current
> version.
>
> In a high-concurrency system, a problem
> that used to be "buffer busy waits" on updates
> only can turn into enqueue waits on updates
> and queries.
>
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> The educated person is not the person
> who can answer the questions, but the
> person who can question the answers -- T. Schick Jr
>
>
> One-day tutorials:
> http://www.jlcomp.demon.co.uk/tutorial.html
>
>
> Three-day seminar:
> see http://www.jlcomp.demon.co.uk/seminar.html
> ____UK___November
>
>
> The Co-operative Oracle Users' FAQ
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Saturday, December 13, 2003 8:19 PM
>
>
> Yep, I also think so. I'm currently developing a small prototype for this
> kind of transparent proxy, which I'll post here when it's stable...
>
> Tanel.
>
> > Tanel,
> >
> > I think this is a good solution, provided the application can handle
> > two phased commit protocol across both the databases, else there
> > could be orphan records on one or both these databases.
> >
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Jonathan Lewis
> INET: jonathan_at_jlcomp.demon.co.uk
>
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-- 
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-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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