Re: RMAN Backup of Standby Database In Managed Recovery Mode

Dennis,

Thanks for the update to the list.

>> if I get pushed toward standby databases, I'll know who to go to. <<

Oh.Oh!

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Friday, May 16, 2003 12:21 PM

> List - Just wanted to report that off-list Arup straightened me out about
> why backing up the standby is a great idea and does not introduce any gaps
> in your recovery capability. He also reported that he has indeed tested
> recovery.
> Thanks Arup and if I get pushed toward standby databases, I'll know who
> to go to.
> Dennis Williams
> DBA, 80%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
>
> -----Original Message-----
> Sent: Thursday, May 15, 2003 6:24 PM
> To: 'ORACLE-L_at_fatcity.com'
>
>
> Arup - Thanks for clarifying that. Just the thought of "we can't tax the
> production server with backups, so we'll backup the standby instead" gives
> me the willies. But you know your environment. Regardless of the answer
you
> get from the manuals on this issue, I would test it. Verify whether you
can
> recover from the backup.
>
> Dennis Williams
> DBA, 80%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
>
> -----Original Message-----
> Sent: Thursday, May 15, 2003 11:32 AM
> To: Multiple recipients of list ORACLE-L
>
>
> Dennis,
>
> Absolutely not! Standby databases are not for throw-away. Since they run
on
> a different server, they RMAN backups from that server will reduce the
load
> on the primary server significantly. Also if your tape backup software
> (Tivoli in my case) uses compression, precious CPU cycles are saved from
the
> primary. So, it's an important part of your overall infrastructure
strategy
> and thus backups from standbny are necessary, not just desirable. Of
course,
> if your standby amounts to, say, 10% of your primary, it may be difficult
to
> run RMAN and tape compression over there.
>
> The issue was not how to take backups from standby database, but rather
the
> confusion created by Notes and Manuals stating that "standby should NOT be
> in managed recovery mode while being backed up". This means for the
duration
> of the backup, which in our case takes 6 hours (2.3 TB, OLTP, 1000
> concurrent sessions), the standby is out of sync with the primary. My
> question was wheether we could backup WHILE in managed recovery mode. And,
> fortunately, the answer is yes.
>
> I have been doing standby databases for years, but the backups were always
> from the primary, so this issue never really arose. At this customer, the
> size of the database, time of backup and insfrastructure prompted me to
> rethink that approach.
>
> HTH.
>
> Arup
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Wednesday, May 14, 2003 3:57 PM
>
>
> > Arup - Sorry you didn't get any replies earlier. The part that confuses
me
> > is what you are trying to accomplish. I've never done a standby
database,
> > only what I've heard in class. But my understanding is that there are
many
> > actions you can take against the primary database that will render the
> > standby unusable. Therefore, the usual issue isn't "how to back up the
> > standby". It is only a copy of the primary, so most people are much more
> > concerned about the primary and consider the standby a "throwaway" since
> it
> > is just a copy of the primary. The usual issue is how to quickly rebuild
> the
> > standby database. I believe that RMAN can help with that because, as you
> > point out, it is good at performing online backups. Robert Freeman has a
> > chapter on how to do that in his book.
> >
> >
> >
> > Dennis Williams
> > DBA, 80%OCP, 100% DBA
> > Lifetouch, Inc.
> > dwilliams_at_lifetouch.com
> >
> > -----Original Message-----
> > Sent: Wednesday, May 14, 2003 11:22 AM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > List,
> >
> > I did not get a response to this question of mine. Meanwhile, I did a
few
> > tests and pestered Oracle Support to provide a definitive answer. The
> latter
> > never happened. However, my tests did reveal a few things. Please read
on
> if
> > you are interested.
> >
> > First, a standby database does not have to be in mounted state while
being
> > backed up by RMAN, contrary to what some notes in Metalink say. The
> standby
> > could be any state - managed recovery or open read only, meaning it was
in
> > INCONSISTENT state. In that state, the restore simply needs more
> > archivedlogs to be conistent, just like a simple RMAN or hot backup,
> nothing
> > special.
> >
> > Second, only the archived logs of standby can be backed up, not the
> primary.
> > While recovering the primary, you can simply use the archived logs from
> the
> > standby, without any problems. Some documentation seems to indicate to
the
> > contrary.
> >
> > In a restore situation you have the following choices.
> >
> > 1. If a datafile of primary is to be restored, merely ftp over the
> datafile
> > from standby, rename it if necesary to the primary's name and recover
that
> > datafile.
> > 2. If the standby datafile is gone, too; restore the RMAN backup of the
> > datafile to the primary and recover it. Remember this backup was taken
at
> > the standby.
> > 3. If archived logs are missing from primary, merely ftp over from the
> > standby or restore directly to primary from backup.
> > 4. If you primary is intact but the standby is broken, instead of
> restoring
> > the standby datafile from tape, place the tablespace in hotbackup mode
in
> > primary and ftp the file over to the standby and perform a manual
> recovery.
> > Then place the standby in managed recovery.
> >
> > I hope this helps.
> >
> > Arup Nanda
> > www.proligence.com <http://www.proligence.com>
> >
> > ----- Original Message -----
> > To: ORACLE-L_at_fatcity.com <mailto:ORACLE-L_at_fatcity.com>
> > Sent: Thursday, May 08, 2003 11:15 PM
> >
> > We run a standby database in managed recovery mode and back the standby
> > using RMAN to save CPU cycles on primary. According to the fine manuals,
> the
> > RMAN backup should be taken off standby after the managed recovery is
> > canceled. Otherwise the backup is "inconsistent", although no further
> > explanation is given what that means and whether that means an "invalid"
> > backup. We currently cancel the managed recovery on standby and then
> > initiate the RMAN backup. Has anyone done the backups without canceling
> > managed recovery mode? I did a few test recoveries and every time the
> > recovery was successful, but I will feel a lot reassured if I hear
someone
> > else has done that.
> >
> > Oracle 8.1.7.4, RMAN Catalog 8.1.7.4, RMAN version 8.1.7.4, Solaris 2.8
> >
> > Thanks a lot in advance.
> >
> > Arup Nanda
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > --
> > Author: DENNIS WILLIAMS
> > INET: DWILLIAMS_at_LIFETOUCH.COM
> >
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> --
> Author: Arup Nanda
> INET: orarup_at_hotmail.com
>
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-- 
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-- 
Author: Arup Nanda
  INET: orarup_at_hotmail.com

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