RE: Fuzzy Operations : Some clarity from Informix

I guess some of my problem is I still some of the systems I support are on hardware that came out 4-6 years ago ... Will >===== Original Message From Rudy Fernandes <rferdy@americasm01.nt.com> ===== >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 ------------------------------------------------------------ This e-mail has been sent to you courtesy of OperaMail, as a free service from Opera Software, makers of the award-winning Web Browser, Opera. Visit us at http://www.opera.com/ or our portal at: http://www.myopera.com/ Your free e-mail account is waiting at: http://www.operamail.com/ ------------------------------------------------------------