Re: quick linux memory question

From: Kenny Payton <k3nnyp_at_gmail.com>
Date: Thu, 3 Apr 2014 14:54:01 -0400
Message-Id: <7991ACFD-D079-4500-A979-438BEFA51544_at_gmail.com>

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] 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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Received on Thu Apr 03 2014 - 20:54:01 CEST