Fw: Fuzzy Operations : Some clarity from Informix

["Vasyl Shulzhenko" <vasilis@softline.kiev.ua>]

----- Original Message -----
From: Rudy Fernandes <rferdy@americasm01.nt.com>
Newsgroups: comp.databases.informix
Sent: 31 ЛЮЪ 2000 Ц. 23:13
Subject: Fuzzy Operations : Some clarity from Informix


> Gang,
>
> Following up on the Fuzzy Operation issue : Specifically, if pages
> affected by fuzzy operations are not physically logged, how will
> recovery be effected in case a crash occurs during a write of a page,
> leaving the page "inconsistent".
>
> The matter was raised with Informix. This is the jist of their reply.
>
> 1. Given that v9.2 no longer physically logs these pages, how will
> recovery in the "partial-write" example be accomplished?
>
> Informix> Restore from a previous backup. However, Informix believes
> that the possibility of a partial-write is negligible to zero.
> Tech-Support knows of no such cases since reduced physical logging was
> first implemented (though not documented) in late v7.2 or v7.3 (the tech
> engineer was not sure about the exact version).
>
> My comments> I confirmed that "reduced" physical logging has been
> implemented in v7.31UC2 on HP10.20. In fact, in the tests I carried out,
> v7.31 carried out identical physical logging as v9.2 under identical
> insert & update scenarios.
>
> 2. If we say that such a partial write scenario is not being catered to
> because the possibility of it occurring is so remote, why do we need the
> physical log at all? All that needs to be done is to locate the point in
> the Logical log where data was last consistent (the latest full
> checkpoint) and apply all transactions from there, finally rolling back
> the un-committed ones.
>
> Informix> This is true. Consideration is being given to getting rid of
> the Physical log in future versions, possibly v9.3.
>
>
> My final comments.
>
> I'm beginning to believe that Informix's original physical logging
> strategy was excellent in situations that existed, say, 10 years ago.
> Improvements in HDD technology and  market pressures from other Database
> Vendor that did not carry out physical logging (and thus had better
> performance) have caused Informix to rethink this strategy.
>
> Cheers
> Rudy
>
>