Hi,
The limit is 4GB per shared memory segment. The SGA can be defined to the amount of memory you have on the machine if the OS implements virtwin calls. For eg: on IBM NUMA using virtwin calls you can define a larger SGA and for one of our benchmarks we had a 9G SGA in 3 shm segments. There is a init.ora parameter on the NUMA use_indirect_data_buffers=true that will enable the usage of these database buffers.I think Solaris also implements virtwin calls.
Hope this helps.
Regards,
Madhavan
>From: Riyaj_Shamsudeen@i2.com
>Reply-To: ORACLE-L@fatcity.com
>To: Multiple recipients of list ORACLE-L
>Subject: Re: What are the Commonly Used SGA Sizes on VLDBs ?
>Date: Wed, 14 Feb 2001 07:05:49 -0800
>
>
>Hi
> There is a 4GB virtual memory limit / process in 32 bit unix systems.
>Oracle attaches the shared memory segments at 0x80000000 by default and
>grows upwards. Since the dlopen calls attaches at 0xEF000000, the limit is
>around 1.73 GB. But you could change the ksms.s module sgabeg variable and
>ask Oracle to attach at say 0x1000000 and which would give you around
>3.7GB. It is pretty simple. Search metalink for the details steps.
>Basically, you edit the ksms.s file change the sgabeg variable value to
>0x10000000 and recompile all the objects.
>
> Limitation is because in 32 bit OS the limit is 4GB. If you want SGA
>size beyound this, then you have to go to 64 bit, where the size is
>virtually limitless.
>Thanks
>Riyaj "Re-yas" Shamsudeen
>Certified Oracle DBA
>"Usual disclaimers apply"
>
>
>
> "Gene Sais"
>
> ach.fl.us> cc:
> Sent by: Subject: Re: What are the Commonly Used SGA Sizes on VLDBs ?
> root@fatcity.com
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>
> 02/14/01 06:55 AM
> Please respond to
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> >>> VIVEK_SHARMA@infy.com 02/14 5:05 AM >>>
>
>What are the Commonly Used SGA Sizes on VLDBs ?
>Answers below:
>
>On SUN E6500 (4u) model , Solaris 2.6 , we are Unable to increase the SGA
>Beyond 1.7 GB on Oracle 7.3.4.5
>
>-->Max size on 32 bit OS and oracle, 2.6 is 32 bit
>
>Qs. What are the ways of increasing the SGA beyond this Limit ?
>--> Upgrade your OS and Oracle to 8i
>
>Qs. What are the Negative Implications of of RE-Creating the Oracle Exe
>With
>a Lowered Base Address to Allow Bigger SGA ?
>--> Good luck on this one
>
>NOTE - This may Give us a Only a Few Hundred MB . What if we Need MORE ?
>
>Qs. Would this Limitaition be on Oracle 8i too ?
>It is a limitation on 32bit vs 64bit oracle and os
>
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> INET: VIVEK_SHARMA@infy.com
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Author: Madhavan Amruthur
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Received on Wed Feb 14 2001 - 10:37:40 CST
