Re: how much cpu on a database rac cluster

From: Mladen Gogala <>
Date: Wed, 5 Sep 2012 09:31:06 +0000 (UTC)
Message-ID: <>

On Wed, 05 Sep 2012 11:00:53 +0300, Jack wrote:

> And very other there is different instance for very good reason.
> Management is also simple/better when having control for one
> business-system per instance.
> N:B. now talkin about non-RAC

I am having problem with understanding this. Why would wasting resources on 10 system tablespaces and 10 instances structures be better management than having only a single instance?

> With different instance you can better agree service time (shutdown)
> when only one plant/division/department to deal with, not the damn
> corporation.

Modern databases typically don't need too much of a maintenance time. At my previous job, single instance databases were run on quarterly maintenance schedule. The last weekend of January, April, July and October were maintenance time. Maintenance duration was from 3AM on Saturday morning till 5AM on Saturday morning, 2 hours. The fact that Oracle releases quarterly patches in the months listed was not a coincidence. Also, you can open physical standby databases for read-only, in case of dire need of access, but that had to be justified. About the only thing that requires an 11G instance to be shut down is patching it. Everything else can be done with only an application blackout.

> And what you save with single instance, some bits. As clever saving as
> putting year into two digit, and get 2000-issues :)
> If separetes instances you can be sure no interfare with each system. Do
> security nor data involvent.

I cannot see how security with 10 databases would be better than the security with a single database. It's a matter of application design. The first rule is: applications never log in as the table owner. The second rule is: every user has his own set of views of sensitive data which doesn't allow him to see or touch anything that he isn't supposed to. I was working on the HIPAA implementation (American law about health care data exchange and privacy) and I know what am I talking about.

> And no extra work to fit sepate systems into one instance, that saves
> money.

Design that uses separate schemas and separate tablespaces would save even more. Most money is saved by not wasting available resources. 10 databases on a single machine wastes resources.

> And the last but not least, you have better control into separeted
> systems.

How? As I've asked you before, if there is a runaway query, you first have to determine the instance that is running it. That might not be so easy, depending on the OS and the platform. How do you compare that with a single query to V$ tables? Finally, you didn't answer my question: do you have a MS Server or Sybase background?

Mladen Gogala
Received on Wed Sep 05 2012 - 04:31:06 CDT

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