Re: oracle memory usage + 11.2.0.1 + RHEL 5
- From: David Roberts <big.dave.roberts@xxxxxxxxxxxxxx>
- To: Chris.Stephens@xxxxxxx
- Date: Tue, 27 Jul 2010 18:14:54 +0100
If you are questioning why the swap space is filling up before memory has
been exhausted; then there are various Unix variants that write the
executable image to swap at the same time that the program is run.
My understanding is that this should result in a greater contiguity with
regards the running code and the image on disk and should lead to
performance improvements and the code is swapped out to disk.
I believe that it's an ELF thing. although there is no theoretical reason
why COFF based systems shouldn't implement the same functionality.
Regards
Dave
On Tue, Jul 27, 2010 at 5:58 PM, Stephens, Chris <Chris.Stephens@xxxxxxx>wrote:
> I got a call from the system administrators yesterday about excessive
> swap usage on one of our database servers. Swapping was not occurring but a
> significant percentage of swap was allocated.
>
>
>
> I recently created an 11.2.0.1 database on the server and configured the
> new memory_target and memory_max_target parameters to 2G. The odd thing is
> that free –m showed a difference of 8GB in memory allocation between the
> database being up and down.
>
>
>
> Reading up on the new auto-memory magic a little indicates that the new
> memory management makes use of /dev/shm.
>
>
>
> Oddly (to me anyways) that is configured to 8gb:
>
>
>
> $ df -k /dev/shm
> Filesystem 1K-blocks Used Available Use% Mounted on
> tmpfs 8153816 625852 7527964 8% /dev/shm
>
>
>
>
>
> I’m struggling with how to explain this.
>
>
>
> That also got me thinking about the usefulness of an a script that
> accurately maps the memory usage of each oracle instance on a particular
> server. In my short reading, it sounds like ‘ps’ isn’t very reliable since
> the memory reported per process also includes shared memory? So, any
> thoughts on the most accurate way to break down the memory consumption of an
> instance and all user processes connected to it?
>
>
>
> Thanks in advance for any insight.
>
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