Re: Multiplexing Datafiles?

"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 Tue Aug 15 2000 - 07:05:45 CDT