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Memory configuration [message #238446]

Fri, 18 May 2007 01:49

california_6_1
Messages: 29
Registered: February 2007

Junior Member

I have a new sun box with 12GB ram. I was wondering, how am i going to configure the /etc/system file for the system memory parameters. what are the recommended configuration and is there a document/guidelines for these? Appreciated if someone please share this.

Many thanks,
cali

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Re: Memory configuration [message #238469 is a reply to message #238446]

Fri, 18 May 2007 03:42

Frank Naude
Messages: 4580
Registered: April 1998

Senior Member

Required settings depend on your OS and Oracle version.
Check the installation guide for detailed instructions.

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Re: Memory configuration [message #238599 is a reply to message #238446]

Fri, 18 May 2007 12:20

california_6_1
Messages: 29
Registered: February 2007

Junior Member

Is there any recommendation as to what needs to be done to configure a server which will host 2 instances with large SGA's? Any oracle documents talking specific about this one rather going the installation document?

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Re: Memory configuration [message #238604 is a reply to message #238446]

Fri, 18 May 2007 12:28

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

>server which will host 2 instances
Then divide recommended values by 2.

[Updated on: Fri, 18 May 2007 12:28] by Moderator

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Re: Memory configuration [message #238627 is a reply to message #238604]

Fri, 18 May 2007 15:32

DreamzZ
Messages: 1666
Registered: May 2007
Location: Dreamzland

Senior Member

Hi,
Is ur os is 64 bit or 32 bit??
Here is the max Sga size you can set for your database.

Operating system-dependent; typically 2 to 4 GB for 32-bit operating systems, and > 4 GB for 64-bit operating systems

[Updated on: Fri, 18 May 2007 15:33]

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Re: Memory configuration [message #238691 is a reply to message #238446]

Sat, 19 May 2007 01:53

california_6_1
Messages: 29
Registered: February 2007

Junior Member

Thanks for your answer DreamZ.

My OS is 64 bit with 12GB Physical ram. or 32 bit??
So what you saying is, if my OS is 64 bit, then the Max shared memory parameter in /etc/system can be greater than 4 GB? What about semaphore and other memory configuration details?

Is there a Oracle recommendation document out here or on metalink which talks this? Appreciated if you refer anything.

Many thanks,
Cali

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Re: Memory configuration [message #238727 is a reply to message #238691]

Sat, 19 May 2007 13:53

DreamzZ
Messages: 1666
Registered: May 2007
Location: Dreamzland

Senior Member

JUST GOTO GOOGLE AND TYPE

ORACLE 10G DATABASE LIMITS

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Re: Memory configuration [message #238740 is a reply to message #238446]

Sat, 19 May 2007 14:44

california_6_1
Messages: 29
Registered: February 2007

Junior Member

My SGA size in init.ora is 8GB and the SHMMAX=4GB in the /etc/system file. What happens, when i try to start the instance?

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Re: Memory configuration [message #238742 is a reply to message #238740]

Sat, 19 May 2007 14:46

Michel Cadot
Messages: 68686
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

You simply can't as you get an error.
Try it.

Regards
Michel

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Re: Memory configuration [message #238885 is a reply to message #238742]

Sun, 20 May 2007 16:23

california_6_1
Messages: 29
Registered: February 2007

Junior Member

So shall i increase the MAXSHARED-Memory setting in /etc/system file to 8GB and try to start my instance? I havent done this. but curious to know, what will happen in this case?

Has anyone tried this scenario before?

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Re: Memory configuration [message #238892 is a reply to message #238446]

Sun, 20 May 2007 19:55

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

Based upon my years of experience the Law of Diminishing Returns applies in Spades to SGA size in relationship to application response time.
If you start with the SGA being really, really small, the response time will be high.
As you increase SGA size, response time will become faster.
If you keep increasing SGA size, respone time will level out.
If you keep increasing SGA size, response time will start increasing.
Never has been & never will be a one size SGA fits all applications. This is irrespective of amount of RAM in the box.

I can guarentee you one thing when it come to Oracle on Solaris.
All RAM will be consumed with a relatively small percentage (<5%) being reported as "free memory"; regardless to total RAM.

Here is a test you can run on your own.
Depopulate the 12GB box down to 4GB.
Start Oracle & run your application under load.
After a couple of hours measure "free memory" & record percentage free memory.
Add RAM to total 8GB & repeat process & record % free memory.
Populate back to 12GB & repeat process & record % free memory.
I am willing to be the % free memory will staty under 5%.
All of this should be done WITHOUT changing any initSID.ora values.
This execise will NOT tell you what the "best" SGA size is.
It simply shows that all available RAM will get used; regardless of the size or proportion of SGA to total RAM.

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Re: Memory configuration [message #238982 is a reply to message #238892]

Mon, 21 May 2007 02:02

california_6_1
Messages: 29
Registered: February 2007

Junior Member

Thanks for your detail answer.

But my question remains the same. I have a SHXMAX memory set to 4GB in /etc/system file and what happens, if i start a oracle instance with 8GB of memory? any ideas?

Thanks,
cali

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