Re: offload backup to standby

From: Mark Bole <makbo_at_pacbell.net>
Date: Thu, 06 May 2004 02:35:13 GMT
Message-ID: <Bvhmc.60720$Ys3.32442@newssvr25.news.prodigy.com>

Howard J. Rogers wrote:

> hrishy wrote:
>

>> Hi All
>>
>> Suppose i have a 3Tb database on the following version of oracle
>>
>> a)9iR2
>> b)817
>> c)7.3.4
>>
>> In 9i R2 we can use datagaurd and releive the primary database and
>> make it available whil the backup window of say 15-18 hours can be
>> utilized without disturbing production on the datagaurd database.
>>
>> I was just wundering can we do anything similar on 817 and 7.3.4
>> versions of standby databases ?

>

[...]
 >(so the replication of redo from primary to the standby is suspended)
>
>

>> Can i create a standby database for 7.3.4 and 8.1.7 and then take a
>> hotbackup 

>
>
> In those other versions, the standby database is not active and
> therefore the concept of hot backup doesn't apply.
>

>> of the secondary databases do a couple of log switches on
>> the primary move it to secondary server and backup them as well..
>> Has anybody implemented such a scenario.
>>
>> I am asking this question out of curiosity wundering anybody has done
>> this kind of a thing?

>
>
> Yes, people have. But it's a long-shot, because the security of your
> data now depends on perfect code in the standby database software
> components. I would certainly be extremely nervous about it in version
> 7, though less so in 8i. But even in 9i, the logical standby doesn't
> work perfectly, so you've got to wonder. It would be better, I think, to
> have an intelligent backup of the primary database, with the standby as,
> er, a standby.
>
> Regards
> HJR
One question, if you already know what you can and want to do under version 9iR2, why ask about previous (de-supported) versions?

Also, I fully agree with the advice to backup tablespaces over time if it is not possible to backup the entire database within the given window.

You can copy all the datafiles, tempfiles, and controlfiles of a physical standby database opened read-only (or closed) under 8i or 9i to another server with the same directory structure (my experience in this regard is with Unix). After doing so (and taking care of init parameters, log directories, etc), you can then open the copy read-only as a physical standby database. In some situations, this is the fastest and easiest way to make a copy (or full backup).

Implied in the note above, you can then un-suspend the physical standby recovery by taking the database out of open read-only mode, either on the original or the copy.

You can also take an export of any or all of the exportable items in the physical standby database while it is open read-only, which then becomes a logical backup. You don't even need the "consistent=y" parameter in this case to get a consistent backup.

--Mark Bole Received on Wed May 05 2004 - 21:35:13 CDT