Re: Combining snapclones with DataGuard

From: sybrandb <>
Date: Tue, 21 Oct 2008 06:20:29 -0700 (PDT)
Message-ID: <>

Comments embedded
> Well, as the original OP, I want to apologize to all. I did not intend
> to cause such a stir.
> Let me provide some lost information: The OS is Windows 2003 64-Bit.
> It is running (64-bit). There are no SANs (yet). The
> potential customer will buy 2 based on the pros/cons capabilities that
> my team outlines. They are a massive company and are planning on true
> enterprise class SANs (to be used to rearchitect the infrastructure.
> It is theoretical now, so saying the "latest & greatest" is not a
> stretch.

So it now appears you are asking to assist you for free, what you get paid for. My-my!
Please in the future note this upfront and I won't bother to respond.

> My goal is simply high-high-level research for disaster recovery
> situational setups for the Oracle portion. There will be >1000miles
> between sites.
> I read Mr. Kaplan's presentation (and yes, I did e-mail him days
> ago ... but no response. I do not feel comfortable calling him via
> telephone). I saw his statement that storage methods of backup are
> "sometimes undiscovered in the world of DBAs". Mr. Kaplan goes on to
> say that array-based replication "Works best in conjunction with Data
> Guard by jointly reducing replication traffic and reducing or
> eliminating single points of failure" .... is he most likely referring
> to non-Oracle database files for the array-based replication, and DG
> for the database?

No, he is not. His referring to SAN level, including database files. Basically his whole presentation is one big plug for products like SnapMirror etc.
Whether Oracle will turn the phone on you, when disaster strikes? Who can tell? Probably Mr. Kaplan won't be there to pay for any damage done.

> Also, Daniel A. Morgan states: "A DR site must be not just a 100%
> clean duplicate of production it must also be logically consistent.
> Something Snapcloning can not guarantee as snapping will efficiently
> replicate corrupt blocks." I have read that DG can be used to detect &
> repair corrupt blocks (
> availability/pdf/corruption_wp.pdf). I have read that snap cloning
> software is able to detect a level of corruption (if it can not read
> the block, it can not propogate it to the destination filer.) Are
> these 2 levels of corruption? (Is DG able to detect a level of
> corruption that snap cloning software can not?

Snap cloning or whatever you call it will probably only perform some basic CRC checks on each disk block.
You provided no information on these products, so this is just a likely guess.
Snapcloning won't know the layout of an Oracle block. So yes, if the most recent version of Dataguard (this definitely doesn't apply to 8i and 9i) is able to detect corruption, it is probably the sort of corruption Snapcloning won't bark about. Reading the doc you provided, Dataguard doesn't repair any corruption silently and automagically, the procedures outlined in the doc will result in downtime, when you are hitting a massive corruption.

My hourly rate is 200 euro.

Sybrand Bakker
Senior Oracle DBA

> Again, thank you for any information.- Tekst uit oorspronkelijk bericht niet weergeven -
> - Tekst uit oorspronkelijk bericht weergeven -
Received on Tue Oct 21 2008 - 08:20:29 CDT

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