Re: Confusion why online redo logs should never be backed up.

Hi Hemant,

I appreciate you're comments but I honestly haven't missed Jared's point and I remain unconvinced. I just don't accept the argument that such backups are warranted in case of junior DBA inabilities to perform clean backups or open with resetlogs. "Junior DBAs" in charge of important production databases that can't do the above are the issue, not the backup strategy. They're just as likely to overwrite the current online logs with the backups during a normal recovery or lock themselves in the toilet or some such ;)

Then again, it might serve the organisation right for employing such DBAs based only on OCP credentials !!

Cheers ;)

Richard
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Monday, May 26, 2003 2:21 AM

>
> Richard,
>
> I think that you are still missing Jared's point.
> It is quite right of you to say that a DBA should do a consistent backup
> and that
> one who does not run his backups properly is committing a sin.
>
> Jared has already explained two examples of why you would want the online
> backups
> included in a Cold Backup. And I reiterate them here.
>
> 1. On Windows, the Stop Oracle Service doesn't always do a SHUTDOWN
NORMAL
> or SHUTDOWN IMMEDIATE. See Bug 1568668
> "With releases 8.1.5 and 8.1.6 stopping the database via the
> services, shuts the database down immediate, whereas 8.1.7
> kills the process. This means recovery is always required on
> startup and customers backup strategies my become invalid.
> If a customer takes cold backups without redo they will not
> be able to open the database. "
> So what happens if you have a database that hasn't been patched and you
> or your colleague or the previous DBA had been happily using the Stop
Service
> and backing up the database without the online redo logs and one day you
> need to recover the database and ..... uh oh ! "Hey ! Why does Oracle
> ask for the redo log file ?!"
>
> 2. You are a consultant or a service provider or are implementing a
system
> for a customer and ask the customer to send you a backup of his database.
> The SA or the trainee-DBA executes a SHUTDOWN ABORT and send you the
database
> files [he might say "I did try a SHUTDOWN but it was 'hanging' for
> 10minutes so I
> finally killed it and ran a SHUTDOWN ABORT before backing up the
database"]
> Always insist that the person at the other end sends you a full backup,
> including
> online redo logs and the init<SID>.ora.
> [Of course, instead of the other person being a customer's SA or
trainee-DBA
> he could be your own colleague [SA/trainee-DBA/Damager] with whom you have
> split the
> responsibility of managing the 50 or 100 odd databases in your enterprise
> or the backup scripts
> may have been written by the former DBA and, although you have reviewed
> and verified or fixed 99 backup scripts in your first 5 days, the 100th
> database
> crashes on your 6th day on the job].
>
>
> I always run a switch logfile or archive log current before backing up
archive
> logs in a Hot Backup but do not backup online redo logs with the Hot
Backup.
> With a Cold Backup I always backup the online redo logs as well. [Tough
luck
> for me if I join an organisation and I am the guy that got hit on that 6th
day
> because the previous DBA's scripts weren't doing a proper shutdown].
>
> Also, although many DBAs know that you can bring up a properly shutdown
and
> backed up cold database without the online redo logs as they know the
> OPEN RESETLOGS command, not all DBAs know this. Suppose the
> person is a trainee-DBA or an SA or a Damager. He's going to curse
> Oracle when he finds that he can't bring up his database although he
> did a "complete" backup [using the guidance provided in the 9iR2 manual
> which so helpfully told him not to backup the online logs but he has never
> read about how and when to run an OPEN RESETLOGS].
>
> Therefore, the advice NOT to backup online redo logs is patently
dangerous.
>
> The advice should be to backup online redo logs already on disk before
> beginning a restore. In fact, that is always a standing instruction in
any
> Oracle Database recovery -- backup what you currently have on disk,
> no matter how badly "hosed" before you begin the recovery.
>
> Hemant
>
>
>
> At 04:56 AM 25-05-03 -0800, you wrote:
> > > Richard,
> > >
> > > You must have missed one. :)
> >
> >Hi Jared,
> >
> >I think we're going to have to introduce quotas, no more than two
> >contributions per thread ;)
> >
> > >
> > > There have been 2 occasions where someone has
> > > sent me 200 gb worth of database on tape, and
> > > the database had not been shutdown properly.
> > >
> > > Since the system datafile needed recovery from
> > > the online logs, I was very glad to have them.
> >
> >I guess my point is that making a backup without shutting down the system
> >properly is a sin akin to scratching a rare David Bowie LP, ie. somewhat
> >unforgivable (although I admit the second sin is far worse). Make a
> >consistent backup and/or have the database in archivelog mode, you then
> >don't require the online redo logs ....
> >
> > >
> > > I have encountered this on a very few other
> > > occasions, but can't recall the circumstances
> > > of those events.
> > >
> > > They are also useful when cloning a DB (without RMAN),
> > > though not required. Depends on how the clone
> > > will be used.
> >
> >I guess my point here is the "though not required" bit. It simplifies the
> >process I agree but even in this case, the online logs are not strictly
> >required.
> >
> > >
> > > As with many things, this is not a black and white
> > > issue. There are shades of gray. While it certainly
> > > not necesssary to normally backup the online logs
> > > during a cold backup, it is incorrect to say that
> > > they are never useful.
> > >
> >
> >I guess we're going to have to agree to disagree. However, getting back
to
> >the subject of sins, including online redo logs in a cold backup is not
> >really an issue that would cause me loss of sleep (unlike scratching DB
> >LPs). Like, it doesn't really hurt. But if someone were to accidentally
> >incorrectly restore them in a recovery scenario, ouch, that would be a
sin
> >worth having a chat about ;)
> >
> >Cheers
> >
> >Richard
> >
> >
> >--
> >Please see the official ORACLE-L FAQ: http://www.orafaq.net
> >--
> >Author: Richard Foote
> > INET: richard.foote_at_bigpond.com
> >
> >Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> >San Diego, California -- Mailing list and web hosting services
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>
> Hemant K Chitale
> Oracle 9i Database Administrator Certified Professional
> My personal web site is : http://hkchital.tripod.com
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Hemant K Chitale
> INET: hkchital_at_singnet.com.sg
>
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-- 
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-- 
Author: Richard Foote
  INET: richard.foote_at_bigpond.com

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