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Re: UNIX root backup/SAN disk image vs. Oracle Hot Backups

From: Howard J. Rogers <hjr_at_dizwell.com>
Date: Sat, 18 Sep 2004 10:28:47 +1000
Message-ID: <414b813a$0$29780$afc38c87@news.optusnet.com.au>


JEDIDIAH wrote:

> On 2004-09-01, Howard J. Rogers <hjr_at_dizwell.com> wrote:

>> Frank Foss wrote:
>>
>>> 
>>> "Ibrahim DOGAN" <idogan_tech_at_yahoo.com> wrote in message
>>> news:6bf58828.0409010559.5ccd70bb_at_posting.google.com...
>>>> Can UNIX root backup or SAN disk image backup be reliable as Oracle
>>>> database backup?
>>>>
>>>> I don't know internals about root backup or disk images but it sounds
>>>> like you may end up with inconsistent control file/datafiles when you
>>>> load them back .
>>>>
>>>> is there anybody out there who knows how root backup/disk image works
>>>> and can tell whether they can replace Oracle hot backups?
>>> 
>>> The concept is developed to reduce the downtime for a cold backup.
>>> A SAN disk image (EMC calls it Business Contingency Volume --BCV)
>>> is an identical synchronized copy of your live filesystem at a point in
>>> time. The connection between the two is broken off, and the live
>>> filesystem goes along doing its thing, while the BCV is static.

> [deletia]
>>
>> I've nothing much to add except that if you're going to break a mirror in
>> order to grab a backup, you don't actually have to shut the database down
>> but can instead use the suspend (and resume) statements.

>
> Why not just put all the tablespaces in backup mode?

How many tablespaces have you got?

So how long do you think it would take you to put all of them into hot backup mode?

(And whereas your answer might be "seconds", someone else's might be "minutes").

And all the time you're trying to get all of them into hot backup mode, the first ones that got there are generating block-sized redo.

That's why.

Now, of course, things change a little in 10g, because in 10g you can say 'alter database begin backup'. And that's one command, and that's just fine.

> If you break
> a mirror and get yourself an inconsistent database, it should be much the
> same as any other inconsistent copy of the database you've created with
> more conventional methods.

Provided you did put the tablespaces into hot backup mode first, one way or another. You cannot simply break a mirror to obtain a guaranteed-usable backup.

Regards
HJR
>
> [deletia]
>
Received on Fri Sep 17 2004 - 19:28:47 CDT

Original text of this message

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