Re: quick linux memory question
Date: Thu, 3 Apr 2014 14:26:44 -0500
Message-ID: <CALrB5ppqAvtJzJPoNki49jixpjNnGB_a5CC4mOvSQ=pQCptnXg_at_mail.gmail.com>
I second what Kenny recommended to set the db parameter use_large_pages=only so you know whether or not the database has the huge pages it needs at startup.
We missed a digit when we were setting up the OS parameters a few years back and learned the hard way when the database starting acting up.
Alfredo
On Thu, Apr 3, 2014 at 1:54 PM, Kenny Payton <k3nnyp_at_gmail.com> wrote:
> Once you're using huge_pages I'd also suggest setting *use_large_pages=only
> *in your database instances. This ensures the database only starts when
> huge pages are available. The risk to not setting this is in the event you
> do not have enough huge pages to start the database and this value is not
> set to only then the database will attempt to start with non huge pages and
> potentialy put you into a memory deprived situation.
>
> Kenny
>
>
>
>
> On Apr 3, 2014, at 2:43 PM, Cunningham, Mike <mcunningham_at_thedoctors.com>
> wrote:
>
> Hi Joe, 252 GB is a respectable amount of memory and like Kenny said you
> should consider using Huge Pages (set in the /etc/sysctl.conf using the
> vm.nr_hugepages parameter). If this were my environment I would be leaving
> around 48GB to the operating system and I would configure the remaining
> 204GB for huge pages. In that case I would be setting the following in
> /etc/sysctl.conf
>
> kernel.shmmax = 219043332096
> kernel.shmall = 66060288
> vm.nr_hugepages = 104448
>
> Also, I would be setting the following in /etc/security/limits.conf
> oracle soft memlock 213909504
> oracle hard memlock 213909504
>
> kernel.shmmax is the maximum size of a single shared memory segment (what
> oracle SGA uses) and is represented in bytes.
> kernel.shmall is the size of shared memory segments in pages. I set this
> number based on the total size of available RAM. You have 252GB. The
> shmall should be calculated using 4096KB page size of the system. So, 252
> GB = 270582939648 bytes / 4096 = 66060288 pages.
>
> I will email you my Virtual Memory Calculator spreadsheet privately. It
> makes it easier and, so far, has never failed me.
>
> Michael Cunningham
> Senior Database Administrator
> The Doctors' Company
> 707.226.0221 - desk
> 707.337.0184 - cell
>
>
>
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org<oracle-l-bounce_at_freelists.org>]
> On Behalf Of Sweetser, Joe
> Sent: Monday, March 31, 2014 11:41 AM
> To: ORACLE-L
> Subject: quick linux memory question
>
> All -
>
> Red Hat Enterprise Linux Server release 5.8 (Tikanga) Oracle 11.1 and 11.2
> databases 252gb main memory Page_size = 4096 (bytes) Shmmax = 76800000000
> (bytes) shmall = 4194304 (pages)
>
> I am sort of referencing Doc ID 301830.1
>
> So, shmmax is about 71.5gb and shmall is currently set to use up to 16gb
> of 'SGA' space (my term).
>
> Sanity check: any issue with setting shmall to something like 15728640
> (60gb)? Still well below physical memory and somewhat below shmmax, but I
> have never set shmall that high so just curious if there any gotchas.
>
> ADVthanksANCE,
> -joe
>
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-- http://www.freelists.org/webpage/oracle-lReceived on Thu Apr 03 2014 - 21:26:44 CEST