Re: Oracle in an AIX LPAR

From: John Smith <john40855_at_gmail.com>
Date: Wed, 4 Mar 2015 10:28:38 -0600
Message-ID: <CALh2JytH5UStED_Y9zGstJk8S2TFfMm+Hm3buZWaO0or3YhNfw_at_mail.gmail.com>

Talking to our system guys, my understanding is that this LPAR has 4 CPU's dedicated, with 2 more allowed, so it is capped at 6. NMON shows 24 CPU's available. As I watch nmon, we see that the first thread on each CPU is typically running at 50% usage or better. I see cpu 9 and 3 getting some usage (second thread on cpu's 3 and 4), but other than that only the first thread on each CPU is being used. I assume the first thread is the primary. SMT 4 is being used.

The processes getting CPU are all oracle<SID> (LOCAL=NO), so sqlnet connections.

On Wed, Mar 4, 2015 at 10:16 AM, Rich Jesse < rjoralist3_at_society.servebeer.com> wrote:

> Hey John,
>
> > This is power7 in a dedicated LPAR.
>
> An LPAR is IBM's term for a VM. So, is there just one LPAR on your POWER7?
> I'd think there'd also be at least 2 more for VIOs, but that's stretching
> my
> knowledge limits...
>
> SMT also comes into play here. By default, the LPAR should be using SMT4,
> which means that 1 virtual CPU core will be shown as 4 logical CPUs. You
> should be able to see this in the "p" screen of nmon.
>
> You mentioned "1 thread per CPU". It sounds like you might be thinking of
> Oracle on Windows? If so, Oracle doesn't run the same in Unix/Linux. The
> background processes will be exposed as individual processes in AIX instead
> of Windows threads in a single process.
>
> Which Oracle process shows at 50% (e.g. using the "u" screen in nmon)?
> That
> could give a big clue...
>
> Let us know!
>
> Rich
>
> > On Wed, Mar 4, 2015 at 9:49 AM, Stefan Koehler <contact_at_soocs.de> wrote:
> >
> >> >> we see that Oracle appears to be using only 1 thread per CPU almost
> all
> >> the time.
> >> You mean one vCPU = one thread, right? The CPU usage can also be shown
> as
> >> 50%, but it is not 50% in reality - it depends on the used entitlement
> per
> >> vCPU.
>
> [snip]
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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Received on Wed Mar 04 2015 - 17:28:38 CET