Re: Physical Memory Fully Used and Swap is Not Used
- From: Mathias Magnusson <mathias.magnusson@xxxxxxxxx>
- To: Mudhalvan Moovarkku <moovarkku.mudhalvan@xxxxxxxxxxxxxxxx>
- Date: Tue, 23 Jun 2009 09:01:22 +0200
As Niall has pointed out memory is measured different on different
platforms. Linux will apparently show you that it uses everything as it
includes dynamically sized areas such as the filecache that idle memory is
used for.
This is why you have the difference in memory reported. You'd have to look
at the DB allications to know what the DB uses, but assuming you didn't
change memory settings you would have as much memory allocated,
Is this a production box? If so, was this problem seen during testing before
the move and if not... What is different now?
If it is a test box and only THEN. Remove all memory settings and have only
PGA and SGA settings. Your default path in 10G ought to be to let Oracle
size memory areas within the amopunt you allocate to PGa and SGA.
Is there a file from the PMON failure that you could upload to Oracle to
have them tell you what went wrong? Having PMON fail even on way undersized
memory allocations would be unusual. If the DB starts, it usually limps
along giving some sessions memory errors, but not a complete instance
failure.
Mathias
On Tue, Jun 23, 2009 at 8:26 AM, Mudhalvan Moovarkku <
moovarkku.mudhalvan@xxxxxxxxxxxxxxxx> wrote:
> Mathias,
>
>
>
> Thanks for your mail.
>
>
>
> Yes I do understand. Now I have two clarifications.
>
>
>
> 1. Problem is at this point instead of using Swap My server response
> time was very slow and PMON process failed with the message at alert “PMON
> failed to acquire latch” and DB went down.
>
>
>
> 2. In 8.0.6 on Unix used only 7GB Memory but why in 10.2.0.4 on
> Linux uses more than 16GB
>
>
>
> Regards
>
> Mudhalvan M.M
>
>
> ------------------------------
>
> *From:* mathiasmag@xxxxxxxxx [mailto:mathiasmag@xxxxxxxxx] *On Behalf Of
> *Mathias
> Magnusson
> *Sent:* Tuesday, June 23, 2009 3:15 PM
> *To:* Mudhalvan Moovarkku
> *Cc:* oracle-l@xxxxxxxxxxxxx
> *Subject:* Re: Physical Memory Fully Used and Swap is Not Used
>
>
>
> Are you trying to tune or to understand memory? There is nothing here that
> would indicate a problem. If you use all you memory and no swap, then that
> would be optimal. It shows that your box is sized perfectly and you do not
> ned to use swap. Using swap reduces performance (if we compare to having
> enough memory and not needing swap).
>
>
>
> If on the other hand you motivation is to understand why these numbers
> would be this way, then someone who has spent more time reading RDAs on
> Linux would need to answer here. To me the numbers would indicate that you
> have just barely reached the point where swap is starting to be used when
> more memory is needed.
>
>
> Mathias
> http://mathiasmagnusson.com
> http://blog.mathiasmagnusson.com
> http://photo.mathiasmagnusson.com
> http://oradbdev.mathiasmagnusson.com
>
> On Tue, Jun 23, 2009 at 7:41 AM, Mudhalvan Moovarkku <
> moovarkku.mudhalvan@xxxxxxxxxxxxxxxx> wrote:
>
> Dear DBAs,
>
> We have recently migrated Oracle from 8.0.6 on HP-Unix to 10.2.0.4
> on Red Hat Linux
>
> Earlier the same application worked fine with 7GB RAM on HP-UNIX
> on PA-RISC
>
> Upgraded system on IBM X 3850 with 16GB RAM but still we have some
> performance issue.
>
> I knew there is some lagging because of Hardware Architecture but
> it is too bad 7 GB to 16GB RAM but still have performance.
>
> Please look at data collected from RDA. Looking at this scenario
> my physical memory is fullly used but Swap is not at all used.
>
> Total Physical Memory 16032 MiB
>
> Available Physical Memory 30 MiB
>
> Swap: Max Size 24575 MiB
>
> Swap: Available 24505 MiB
>
> Swap: In Use 70 MiB
>
> We know there is some performance issue in application. I would
> like to make as much as possible from Database/Linux side tunning to provide
> atlease peaceful performance. Can any body through some light on why the
> swap is not at all used.
>
> Regards
>
> Mudhalvan M.M
>
>
>
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