Re: New challenge - clustering - do I understand this correctly?

Ed Stevens <nospam_at_noway.nohow> wrote in message news:<jo4gjvsv17mr0j8jqo2p7a04pbb5c6s7bg_at_4ax.com>...

> With OPS, you have two concurrently instances against the same
> database. They can both be accessed concurrently for load balancing
> or whatever. If one fails, SQLNet (if correctly configured) will
> reconnect everything to the surviving instance.

which will then rollback any interrupted transactions in the failed instance, as well as releasing locks, etcetc.

>
> Do I have this right?

In a nut shell, yes.

> If so, are there pros and cons that might not be immediately obvious.

HA won't scale without replacing hardware by faster/more capacity one.

OPS/RAC won't scale linearly for heavy concurrent update activity, but this can be compensated for by design. Otherwise, just add more of the same boxes at any time.

> What I see is that the HA option can result in a few minutes of outage
> during the switch, but is much easier for the DBA to adminster -- it
> would be handled just like any other single machine DB and all cluster
> activity and recovery from node failure is handled by the OS --
> transparent to Oracle. On the other hand the OPS option is more
> complicated for the DBA to administer, but can result in near zero
> down time.

I don't understand how you can think RAC/OPS is harder on the administrator. All that happens is that a second instance recovers transactions from the failed instance. All else runs along same old same old. What in that requires "complication" from the administrator?

Now if you're talking *setup*, yes, there is a possibility things will be slightly more complex to get started with RAC. But that is a once-only effort: hire a good reputation consultancy to help you with it and be done. That's where consultants add value: once-only requirements.

As for efficiency, picture this:

• you get a new car.
• your wife gets a new car.
• you follow your wife everywhere a coupla minutes behind her, so that you can pick her up if something goes wrong with her car.
• she does the same to you.

or

• you buy a new car.
• your wife buys a new car.
• you go to work, she goes shopping.
• any probs, one of you calls the other and picks him/her up.

Which option would you rather?
<okok, no "Antonio Banderas" replies!> :D

Cheers
Nuno Souto
wizofoz2k_at_yahoo.com.au.nospam Received on Mon Aug 11 2003 - 22:36:24 CDT