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MAX SGA Limit on Linux 32-bit [message #461746] Mon, 21 June 2010 05:07 Go to next message
paradoxkhan
Messages: 92
Registered: April 2008
Location: Pakistan
Member
Hi,

I need to increase the SGA of my oracle 10g(10.2.0.4) to 3Gb which is currently set to 1.15Gb. Please clarify, Is there any restriction on increasing SGA on Linux 5.3 32-bit Architecture? If Yes, Then to what maximum value we can set the SGA? Below is Os details.

>cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.3 (Tikanga)

>uname -r
2.6.18-128.el5PAE

> uname -a
Linux 2.6.18-128.el5PAE #1 SMP Wed Jan 21 08:28:30 EST 2009 i686 i686 i386 GNU/Linux

waiting for reply.

Thanks

[Updated on: Mon, 21 June 2010 05:11]

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Re: MAX SGA Limit on Linux 32-bit [message #461776 is a reply to message #461746] Mon, 21 June 2010 07:36 Go to previous messageGo to next message
mkounalis
Messages: 146
Registered: October 2009
Location: Dallas, TX
Senior Member
The standard max size (I have found) for a sga on 32-bit linux is about 1.7 gb. You can configure huge pages and other things in the Linux kernel to get to about 2.5 gb. Here is an article I found through google that I wish I had way back when I had to deal with this:

http://www.puschitz.com/TuningLinuxForOracle.shtml

How much ram is configured in your Linux box? What led you to think that you need a 3gb sga? Why on earth are you not running a 64-bit system?

[Updated on: Mon, 21 June 2010 07:37]

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Re: MAX SGA Limit on Linux 32-bit [message #461781 is a reply to message #461776] Mon, 21 June 2010 08:21 Go to previous messageGo to next message
paradoxkhan
Messages: 92
Registered: April 2008
Location: Pakistan
Member

I have 8Gb Ram. It is planned to move to 64-bit in future. But as far need to go with the same. we are facing some db performance issues. ADDM and by seeing AWR we have planned to increase sga. I'm reviewing Link you have referred, But quick word, can i increase sga to 3Gb by seeing my box configuration?

Thanks
Re: MAX SGA Limit on Linux 32-bit [message #461790 is a reply to message #461781] Mon, 21 June 2010 08:51 Go to previous messageGo to next message
BlackSwan
Messages: 22690
Registered: January 2009
Senior Member
post formatted results from following SQL

SELECT * FROM V$SGA_TARGET_ADVICE
Re: MAX SGA Limit on Linux 32-bit [message #461805 is a reply to message #461781] Mon, 21 June 2010 10:50 Go to previous messageGo to next message
mkounalis
Messages: 146
Registered: October 2009
Location: Dallas, TX
Senior Member
paradoxkhan wrote on Mon, 21 June 2010 08:21

I have 8Gb Ram. It is planned to move to 64-bit in future. But as far need to go with the same. we are facing some db performance issues. ADDM and by seeing AWR we have planned to increase sga. I'm reviewing Link you have referred, But quick word, can i increase sga to 3Gb by seeing my box configuration?

Thanks


Short answer? No. Not even close. Again - 1.7 is pretty much the top end. The document describes how you can tweak various Linux kernel settings to allow you to move up over 2.5 (the article says 2.7 but I have never personally seen that . . . . ) but I have to say, it's a lot of work - and if this is a production system you are probably better off not fiddling with Linux kernel stuff as it takes a lot of reboot-iterations to nail down. If you have an exact mirror system for test/dev/qa then you might be able to tweak your kernel there and then mimic it in production . . . but again, it's a lot of work. There is a way to move the buffer cache into extended memory - but there are limitations for doing that. Remember - 32-bit means a max of 4gb of addressable memory. There is no magic to get around this - just some smoke and mirrors to band-aid it. A process needs to map in the Linux kernel memory structures to be able to talk to the various I/O devices you have configured - and by the way you are also going to be dealing with the low_mem 32-bit Linux kernel issue as well if you try and get the SGA up past 1.7 gb.

Good luck!
Re: MAX SGA Limit on Linux 32-bit [message #462279 is a reply to message #461805] Wed, 23 June 2010 06:19 Go to previous message
paradoxkhan
Messages: 92
Registered: April 2008
Location: Pakistan
Member
Ok thanks. we are going on 64bit system from 32-bit. Need to clear one thing.
we are going to take full expdp from current 32bit with user system and then after preparing 64bit box
we will import it there.
If we import full database all the users will be created automatically? no need to create users, only tablespaces needed to create before dpimport?
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