Re: Backup flashback logs to tape

On Jul 5, 8:40 pm, zigzag..._at_yahoo.com wrote:
> On Jul 5, 12:26 pm, zigzag..._at_yahoo.com wrote:
>
>
>
> > On Jul 5, 9:36 am, DA Morgan <damor..._at_psoug.org> wrote:
>
> > > Ganesh wrote:
> > > > I am very sorry my thread started all this mud sledging. I have
> > > > started working on ORACLE just a couple of months ago. No document
> > > > provided answers to my questions and hence I posted them here. If
> > > > someone claims any document has answerws to these questions, please
> > > > provide me the link.
>
> > > > But the positives I have got from my investigation and this
> > > > discussion:
>
> > > > 1. Flashback logs are more of a nice to have feature and its okay if
> > > > we don't back them up as they are not required for recovery.
>
> > > You sure didn't get that from me. I consider Flashback logs 100%
> > > required for production databases.
>
> > > What I've seen in this thread is a remarkable lack of understanding
> > > of how and when to use Flashback Database and Restore Point technology:
> > > They are absolutely brilliant.
>
> > > Think of Flashback Database as a fire extinguisher. It may sit there
> > > for years not being used but its value is that it is there if you need
> > > it. Here's an example of where/how to use Flashback Database.
>
> > > You receive from your application vendor a script that modifies the
> > > application's database layer or you have been tasked with performing
> > > an upgrade of an internally developed application.
>
> > > Step 1: Create a Guaranteed Restore Point
> > > Step 2: Perform the upgrade
> > > Step 3: Test
> > > Step 4: If anything failed Flashback Database
>
> > > The difference in space and time required to do a Level 0 backup at
> > > Step one versus using Flashback is immense. At Step 4, again, Flashback
> > > is superior in every respect.
>
> > > > 2. There is no command / workaround ORACLE provides for backing up
> > > > Flashback logs to TAPE.
>
> > > As there is no need to back them up ... no.
>
> > > > 3. Given this if you still want to backup Flashback Logs its going to
> > > > be a very tricky operation.
>
> > > Only if you use ASM and only if you are incapable of using the
> > > technology Oracle has provided to copy them to somewhere that can be
> > > backed up onto tape.
>
> > > So I'd say you've got it 99% incorrect.
> > > --
> > > Daniel A. Morgan
> > > University of Washington
> > > damor..._at_x.washington.edu (replace x with u to respond)
> > > Puget Sound Oracle Users Groupwww.psoug.org
>
> > Can you elabrarate on 3 because Metalink support never pointed that
> > out. to me
> > when I asked them about backing up flashback logs.- Hide quoted text -
>
> > - Show quoted text -
>
> Also regarding 2 (there is no need to backup), I pointed out a hole in
> design what happens if disk carshes (where flashback logs are
> stotred) or some flashback logs are accidently deleted, one may then
> have to rest flashback database by turing it off and on and lossing
> all falshback logs.

So what? Flashback logs are not essential for recovery, they are more like an incremental cold backup of your database slowly rolling forward in time and trying to postpone this roll forward to guarantee all guaranteed restore points as FRA space permits. If you lost them - well, no big deal, you still have your level 0 backup and archived redo that you can use for normal recovery, don't you? Surely it will be slower and less convenient than a single FLASHBACK DATABASE command, but tell me how often did you use this command in production in the last year? Or did normal recovery?

Daniel's analogy to a fire extinguisher is very good, only fire extinguishers are not that expensive. :) This feature is a very nice addition to standard recovery options, but it's not essential for recovery and it's pretty expensive disk space wise. A must have if you can afford it, but expendable if you are on a tight budget and can't provision enough storage for the FRA to guarantee your restore points (and that space better be reliable...) Ability to flashback is not something to mourn for when lost anyway. :)

My $0.02.

Regards,

   Vladimir M. Zakharychev
   N-Networks, makers of Dynamic PSP(tm)    http://www.dynamicpsp.com Received on Thu Jul 05 2007 - 12:34:58 CDT