Re: Multiplexing Datafiles?

Raw nerve or what...

"Howard J. Rogers" <howardjr_at_www.com> wrote in message news:399931e8_at_news.iprimus.com.au...
>
> "Adrian Shepherd" <theshepherds_at_hotmail.com> wrote in message
> news:Tx8m5.89106$N4.2157364_at_ozemail.com.au...
> > Obviously you are expressing an oppinion but in more informed scenario
 it
 is
> > quite possible for a database with a couple of GB of datafiles or less
 to
> > generate much more redo that the size of the databse, there is no
> > correlation whatsoever between the amount of redo generated and the size
 of
> > the datafiles. I have often pondrered the suitability of mirrored
 datafiles
> > in many environments, your failure to grasp this theoretical fundamental
> > approach instead of archiving leads your argument to be too focused.
 Accept
> > that the original poster and myself and probably many other experienced
 and
> > broad minded DBA's do see a requirement for this and would still like to
 see
> > it happen.
>
>
> Look. Quite frankly I don't give a damn about what you would like to see
> happen in Oracle. The fact is, the guy asked whether it was possible and
 it
> isn't. Deal with it.
>
> I gave you the answer for the situation you describe: small data files and
> large amounts of redo. Don't run it in archivelog mode, and use external,
> hardware mirroring. What you or I would wish were possible is entirely
> beside the point. The solution is there. Just don't look for it in
 Oracle.
>
> In case you missed the point: I deal in trying to answer people's
 questions
> factually, and not in wish-lists.
>
> >
> > We should at least have the option. And I beleive Oracle stands to gain
 in
> > offering a more comprehensive set of options , it broadens their
 suitability
> > to more customers.
> >
>
> "Should". "Believe". Clearly Larry is entirely wrong in ignoring your
> requirements, and is likely to be paupered as a result. Not.
>
> Whatever: I don't care what you would LIKE to see. The facility is not
> there. Buy a RAID subsystem and do your own mirroring -Oracle isn't
> stopping you. And that option has been available to you since, oh...
 around
> Oracle 1.0?
>
> > Of course it doesn't help if the current negativity feeds back to
 Oracle,
 to
> > re-iterate , you may not see a reason to, but others do.
>
> Try to stick to speaking for your own opinion and not for others (heaps of
> which I have yet to see). Also, try not to lard your posts with insults
> such as 'your failure to grasp' or "more informed"... it makes your own
> "arguments" look like subjective clap-trap.
> HJR
>
> >You have technical
> > arguments against it in your real world experience, but that is far from
 all
> > encompassing.
> >
>
>
> >
> > "Howard J. Rogers" <howardjr_at_www.com> wrote in message
> > news:39990d4d_at_news.iprimus.com.au...
> > >
> > > "Adrian Shepherd" <theshepherds_at_ozemail.com.au> wrote in message
> > > news:jyRl5.88176$N4.2136496_at_ozemail.com.au...
> > > > What if I want to multiplex datafiles in my database but not run in
> > > > ARCHIVELOG mode for some reason, perhaps because the database would
 generate
> > > > too much archive or if the database is a warehouse that isn't suited
 for
> > > > ARCHIVELOG mode ?
> > > >
> > > > Multiplexing datafiles seem's a good enough request for me, and more
 to
 the
> > > > point , redo logs DO NOT supply all the protection you need, perhaps
 you
> > > > meant archived redo ?
> > > >
> > >
> > > You'll have to explain why providing all the redo since the time of
 the
 last
> > > backup doesn't provide you with all the protection you require. I
 made
 no
> > > distinction between on-line or archived redo in that statement, and
 rightly
> > > so. I also talked about 'mirroring your redo'. Loose terminology, I
> > > guess -but since Oracle 8, it's been possible not only to mirror your
> > > on-line logs, but also to 'mirror' your
 archives -log_archive_duplex_dest
> > > for example. Again, I make no distinction between online and archived
> > > logs -the fact is, protecting ALL your redo is all you need to ensure
 total
> > > data recovery.
> > >
> > > Since it remains a fact that providing all required redo since the
 time
 of
> > > the last backup guarantees that you will never lose a single committed
> > > transaction, I don't quite see what extra protection you'd need or
 want.
> > >
> > > Your proposed solution seems perverse. Instead of generating
 gigabytes
 of
> > > redo each day, you want to mirror tens or hundreds of gigabytes of
 datafile.
> > > I know which I would prefer to do if disk space was tight.
> > >
> > > Whatever. The fact remains, wishlists notwithstanding, there is no
 facility
> > > in Oracle to mirror datafiles within a single database (standby
 databases
> > > etc are a different sort of technology entirely, and are designed to
 solve
> > > different problems), and neither does there need to be.
> > >
> > > You are of course entirely free to put the database back into
 noarchivelog
> > > mode, and use external hardware mirroring to protect your datafiles.
> > >
> > > Regards
> > > HJR
> > >
> > >
> > >
> > >
> > > >
> > > > "Howard J. Rogers" <howardjr_at_www.com> wrote in message
> > > > news:3995df0c$1_at_news.iprimus.com.au...
> > > > >
> > > > > "Rob Jolliffe" <rjolliffe_at_my-deja.com> wrote in message
> > > > > news:8n4295$mqp$1_at_nnrp1.deja.com...
> > > > > > Hi,
> > > > > >
> > > > > > I'm just beginning to learn Oracle, and I was reviewing some
 Email
> > > > > > regarding Raid5 vs Raid0 performance. It seems Raid 0 is
 significantly
> > > > > > better for performance - but you lose the redundancy of Raid 5
 (or
 even
> > > > > > Raid 1).
> > > > > >
> > > > > > I was trying to also determine if in a data tablespace it is
 possible
 to
> > > > > > multiplex (mirror) datafiles the same way you can with a Redo
 log
 group.
> > > > > > I was totally unable to determine if you are or are not.
> > > > > >
> > > > >
> > > > > Absolutely not. Never has been, and there never will be -because
 it
 is
> > > > > entirely pointless. The reason for duplexing your data files is,
> > > > > presumably, to avoid complete disaster in the event that one of
 them
 dies,
> > > > > gets deleted, corrupted etc. That is precisely what the Redo Logs
 are
 there
> > > > > for. Provided you've kept all your redo since the time of the
 last
 backup,
> > > > > you can reconstruct any given data file up to the precise time of
 failure.
> > > > >
> > > > > So if you're mirroring your Redo, you have provided all the
 protection
 your
> > > > > data files ever need.
> > > > >
> > > > > (Conceivably, you can use external, hardware mirroring of data
 files
 to
> > > > > enable recovery to take place *faster* -you just break the mirror
 and
 use
> > > > > the good copy. No need to wait for all that Redo to be re-played.
 But
> > > > > that's a mean-time-to-recovery issue. It's certainly not
 necessary).
> > > > >
> > > > > > Can anyone tell me? I know you can stripe tablespaces - but can
 you
> > > > > > mirror them? Perhaps this requires creating two tablespaces and
 somehow
> > > > > > matching them?
> > > > > >
> > > > >
> > > > > Forget it. There's no such concept in Oracle, because the Redo
 does
 all
 the
> > > > > protection work we need.
> > > > >
> > > > > Regards
> > > > > HJR
> > > > >
> > > > >
> > > > >
> > > > > > Thanks very much
> > > > > >
> > > > > > -Rob
> > > > > >
> > > > > >
> > > > > > =============
> > > > > > From the desk of Rob Jolliffe
> > > > > >
> > > > > >
> > > > > > Sent via Deja.com http://www.deja.com/
> > > > > > Before you buy.
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
> >
>
>
Received on Thu Aug 17 2000 - 08:48:30 CDT