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SGA Sizing [message #322266] Thu, 22 May 2008 23:33 Go to next message
hexmanju
Messages: 71
Registered: September 2005
Location: MUMBAI
Member
Hi

Long time doubt ?

In Oracle Database when we specify the SGA size thru(SGA_MAX_SIZE) or SGA_TARGET(10g)equal to 8GB and say we have
physical memory of 4GB does it throw out of memory error.Say if i have allocated Virtual memory in addition to physical memory of 8GB more,will it be making use of that for the memory deficiency

How does Oracle Handle memory utilisation?

Thanks
MM
Re: SGA Sizing [message #322267 is a reply to message #322266] Thu, 22 May 2008 23:36 Go to previous messageGo to next message
BlackSwan
Messages: 25046
Registered: January 2009
Location: SoCal
Senior Member
>How does Oracle Handle memory utilisation?
Oracle handles it well.

Why are you fixated on memory utilization?
Re: SGA Sizing [message #322289 is a reply to message #322266] Fri, 23 May 2008 00:28 Go to previous messageGo to next message
abs_amit
Messages: 59
Registered: January 2006
Location: delhi
Member
first of All please explain
why you want SGA size 8GB?
what is the database size?
which operating system you are using ? (32bit or 64bit)

Regards
Amit Yadav
Re: SGA Sizing [message #322771 is a reply to message #322289] Mon, 26 May 2008 03:43 Go to previous messageGo to next message
hexmanju
Messages: 71
Registered: September 2005
Location: MUMBAI
Member
I am just interested to know if Entire SGA fits in RAM..So i wanted to make it 8GB .My OS is 32-bit Micrsoft Windows.
Re: SGA Sizing [message #322788 is a reply to message #322266] Mon, 26 May 2008 04:24 Go to previous messageGo to next message
varu123
Messages: 754
Registered: October 2007
Senior Member
Quote:
I am just interested to know if Entire SGA fits in RAM.

Entire SGA has to be fit in RAM.
Re: SGA Sizing [message #322817 is a reply to message #322788] Mon, 26 May 2008 05:41 Go to previous messageGo to next message
abs_amit
Messages: 59
Registered: January 2006
Location: delhi
Member
It makes use of free (RAM + virtual/paging memory) while starting the instance

But its always better to let total SGA to be fit in RAM only.
Also remember that 100% RAM is not for the SGA only and also consider other processes which consume the RAM.

Windows OS requires 20% of RAM to work
Unix OS requires 10% of RAM.

So total RAM which can be allocated to SGA in windows OS is 80% and unix Os is 90%

We should also leave some RAM for individual oracle connections.
each oracle connection will use two megabytes of RAM plus (sort_area_size plus hash_area_size (or pga_aggregate_target)).

But the better practice is:

SGA size should not be more than 50% of RAM.

2GB SGA size should be sufficient for high transaction and big database. Still you can generate statistics later and tune it.


can also refer the below link for more details:
"http://www.dba-oracle.com/art_dbazine_ram.htm"


Regards
Amit Yadav
Re: SGA Sizing [message #323792 is a reply to message #322817] Thu, 29 May 2008 08:33 Go to previous message
hexmanju
Messages: 71
Registered: September 2005
Location: MUMBAI
Member
Thanks for this Reply..It helps.
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