Re: Stateless clients and locking schemes (or rather isolation levels)

From: BobTheDataBaseBoy <"xxx>
Date: Thu, 28 Jul 2005 22:55:30 -0400
Message-ID: <AJWdnVQIdeEaB3TfRVn-3Q@rcn.net>

Serge Rielau wrote:
> Superboer wrote:
>

>>> This is a funny way of looking at. Obviously Oracle's none locking
>>> engine is perfectly suited to scaling multi user applications,
>>> particularly when most people are developing for stateless clients.
>>
>>
>>
>> ahum does the above explain why informix was faster on a 5 times
>> smaller machine then obstacle...????
>>
>> Superboer.
>>

> Changed the subject lines and following up on what Knut started.
>
> How does Oracles snapshot isolation help with stateless clients.
> To the best of my knowledge snapshot semantics only operate on either a
> statement or a transaction level. In a stateless scenario I'd assume
> that teh application transaction covers at least two database
> transactions. A read phase wher the resultset is displayed at the client
> and a separate write phase where the modified data is written back.
> How does snapshot isolation help here?
> Informix supports versioning columns which can be used by the app to
> prevent overwriting other users changes across DB transaction boundaries.
> MS SQL server has a somewhat similar approach and even buried optimistic
> locking into the cursor logic (not applicable in a stateless enviroment
> (no cursor open).
> I see tha value of snapshot isolation for certain purposes. I don't see
> it for a 3 tier web application....

well. may be not. i went back to Weikum/Vossen, chapter 5. sounds like   an approach. and a google for +multiversion +concurrency +"3 tier" came up with this. kind of funny, really.

http://sapdb.2scale.net/moin.cgi/FeatureEnhanceProposals

BTDBB
>
> Thoughts?
> Cheers
> Serge
Received on Thu Jul 28 2005 - 21:55:30 CDT