RE: SHMMAX setting on Sun 4800 box

Matt,

Your SGA can still be larger than 4G even if SHMMAX is not larger than 4G. When SGA size > SHMMAX, mutilple shared memeory segements will be allocated. There used to be a claim that if you can fit the SGA into a single shared memory segment, ISM will be used. This might be true for older version of Solaris, but I have seen ISM being used even when mutiple shared memory segments are allocated on Solaris 8.

Regards,

Richard

-----Original Message-----
Sent: Thursday, June 26, 2003 10:55 AM
To: Multiple recipients of list ORACLE-L

As long as you're running 64-bit solaris and 64-bit oracle, you can set SHMMAX to be larger than 4G, which will allow your SGA to be larger than 4G. Keep an eye on your overall memory pressure, though, to make sure you don't oversubscribe the system. If you're running Solaris 8/9 and/or using some sort of direct i/o (raw devices, veritas, etc.) you're good to go at that point. If you're running 7 or 2.6 (can you even run 2.6 and 7 on the 4800? I doubt it), you'll want to turn on priority_paging in /etc/system to keep your sga from getting paged out in favor of filesystem buffers.

Thanks,
Matt

--
Matthew Zito
GridApp Systems
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> -----Original Message-----

> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On 

> Behalf Of Zhai Jingmin

> Sent: Thursday, June 26, 2003 5:34 AM

> To: Multiple recipients of list ORACLE-L

> Subject: SHMMAX setting on Sun 4800 box

> 

> 

> Hello, List,

> 

> Our Sun Fire 4800 server have 8 CPUs and 16G memory.I set the 

> SHMMAX kernel parameter to 4294967295 according to 

> installation guide on metalink.The SHMMAX is "max shared 

> memory segment size".What's the relationship between SHMMAX 

> and max size of SGA?Because our oracle's SGA may exceed 

> 4G,can I set this parameter to 8G,10G?

> 

> Any suggestion is appreciated.

> 

> Thanks, 

> 

> Zhai Jingmin

> [EMAIL PROTECTED]

> 2003-06-26

> 

> 

> 

> -- 

> Please see the official ORACLE-L FAQ: http://www.orafaq.net

> -- 

> Author: Zhai Jingmin

>   INET: [EMAIL PROTECTED]

> 

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