RE: quick linux memory question
- From: "Cunningham, Mike" <mcunningham@xxxxxxxxxxxxxx>
- To: "JSweetser@xxxxxxxx" <JSweetser@xxxxxxxx>, ORACLE-L <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 3 Apr 2014 11:43:03 -0700
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@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] 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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