Re: SGA bigger than 50G
From: Yong Huang <yong321_at_yahoo.com>
Date: Fri, 7 May 2010 07:54:51 -0700 (PDT)
Message-ID: <355919.2761.qm_at_web80608.mail.mud.yahoo.com>
> As for huge pages, you need to configure just a little bit more than
> what you need for the SGA (PGA won't use huge pages). For example, if
> you want to use an SGA of 30gb, you'd configure huge pages to be
> 30gb + a few tens of MBs to allow for a bit of overhead.
>
> Harel
Date: Fri, 7 May 2010 07:54:51 -0700 (PDT)
Message-ID: <355919.2761.qm_at_web80608.mail.mud.yahoo.com>
> As for huge pages, you need to configure just a little bit more than
> what you need for the SGA (PGA won't use huge pages). For example, if
> you want to use an SGA of 30gb, you'd configure huge pages to be
> 30gb + a few tens of MBs to allow for a bit of overhead.
>
> Harel
I agree. It's better to make sure the HugePages memory covers all instances simultaneously running on the box, including ASM if available. HugePages is guaranteed to be locked in physical memory regardless its version. Any unused bit of it is wasted. I have some write-up about this topic at
http://yong321.freeshell.org/oranotes/HugePages.txt
By the way, 50GB SGA on a 64GB box is not a wise decision as others said. Every bit of increase in PGA is benefitial for hashing (but not sorting) when it's in one-pass phase, common to a data warehouse.
Yong Huang
-- http://www.freelists.org/webpage/oracle-lReceived on Fri May 07 2010 - 09:54:51 CDT