Re: shmall on Linux recommendation
- From: Surachart Opun <surachart@xxxxxxxxx>
- To: Dave.Herring@xxxxxxxxxx
- Date: Tue, 12 Jan 2010 23:12:25 +0700
If you use SGA = 17 GB , shmall should be 4456448 ).
If you set it less than ... you will see
SQL> startup
ORA-27102: out of memory
Linux-x86_64 Error: 28: No space left on device
http://surachartopun.com/2009/10/shared-memory-tuning-startup-database.html
If you're finding out other doc (except doc 301830.1)
Tuning Red Hat Enterprise Linux: Oracle and Oracle
RAC<http://www.redhat.com/f/pdf/summit/scroft_240_turning_rhel_for_oracle.pdf>
mem=$(free|grep Mem|awk '{print$2}')
totmem=$(echo "$mem*1024"|bc)
huge=$(grep Hugepagesize /proc/meminfo|awk '{print $2}')
max=$(echo "$totmem*75/100"|bc)
all=$(echo "$max/$huge"|bc)
echo "kernel.shmmax = $max"
echo "kernel.shmall = $all"
>Sizing shmall to be the SUM of the SGAs on the server makes sense, but I'm
curious if anyone has experience that suggests otherwise? Also, can anyone
think of a good reason to set shmall to RAM + swap (other than "'cuz it's
there")?
I don't use SWAP to calculate. I use only Physical memory. and SWAP is DISK
anyway.
Good Luck
Surachart Opun
http://surachartopun.com
On Tue, Jan 12, 2010 at 10:54 PM, Herring Dave - dherri <
Dave.Herring@xxxxxxxxxx> wrote:
> Folks, I've inherited a 4-node RAC plus DG environment that has a rather
> curious shmall setting that I'd appreciate your thoughts on. I've done my
> best to understand it's current setting but those that made the decision are
> no longer with the company and/or client.
>
> The system is running 10.2.0.2 on RHEL 4. Like I said, it's a 4-node RAC,
> 64 GB RAM, with the same for a physical standby. Currently the SGA of each
> instance is 17 GB.
>
> The install guide gives a minimum value of 2097152 (8 GB) while the current
> value is 25165824 (96 GB). To me it seems just a wee bit aggressive to be
> setting the total shared memory to be RAM + swap! MOS doc 301830.1 gives
> the recommendation of the SUM SGAs on the server, so in this case 4456448
> (17 GB).
>
> Sizing shmall to be the SUM of the SGAs on the server makes sense, but I'm
> curious if anyone has experience that suggests otherwise? Also, can anyone
> think of a good reason to set shmall to RAM + swap (other than "'cuz it's
> there")?
>
> Thx.
>
> Dave Herring | DBA, Acxiom Database Services
>
> 630-944-4762 office | 630-430-5988 cell | 630-944-4989 fax
> 1501 Opus Pl | Downers Grove, IL, 60515 | U.S.A. | www.acxiom.com
> Service Desk: 888-243-4566
>
>
>
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