Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Mailing Lists -> Oracle-L -> RE: SHMMAX setting with multiple instances? Solaris 2.8,Oracle 8.1.7.4

RE: SHMMAX setting with multiple instances? Solaris 2.8,Oracle 8.1.7.4

From: Bobak, Mark <Mark.Bobak_at_il.proquest.com>
Date: Fri, 13 Feb 2004 11:06:07 -0500
Message-ID: <4C9B6FDA0B06FE4DAF5918BBF0AD82CF03B4525E@bosmail00.bos.il.pqe>


Er, regarding ISM, what I meant to say was: The rumor states that unless your SGA is in one contiguous shared memory = segment, Solaris won't use ISM. That is false. ISM will be used = regardless of whether the SGA is broken into multiple shared memory = segments.

-Mark

-----Original Message-----
From: Bobak, Mark=20
Sent: Friday, February 13, 2004 10:53 AM To: oracle-l_at_freelists.org
Subject: RE: SHMMAX setting with multiple instances? Solaris 2.8,Oracle 8.1.7.4

Carmen,

SHMMAX determines the largest size a single shared memory segment can = =3D
be. It does NOT govern the total amount of shared memory that can be = =3D
allocated, just the max allowable size of a single chunk.

The value you show, 4,294,967,295 (shown w/ commas to demonstrate it's = =3D
4GB-1, not 400MB) is fine. In a 32 bit
environment, 4GB is the largest amount of memory that a program can =3D address, since 2^32=3D3D4GB.

So, if your Oracle installation is 32-bit code, that value is more than = =3D
enough. Even if it was 64-bit code, and you specified an SGA larger =3D than 4GB, having SHMMAX set to 4,294,967,295 would not harm you. You = =3D
would just see that your SGA was made up of multiple shared memory =3D segments. (Do 'ipcs -m' on Solaris to see all the shared memory =3D segments.) Note that there has been a vicious rumor that Solaris must = =3D
have your entire SGA in a single shared memory segment, if ISM (Intimate = =3D
Shared Memory) would be disabled. This is NOT TRUE. There is no harm = =3D
in having your SGA in multiple shared memory segments.

Bottom line, you should go ahead with:
set shmsys:shminfo_shmmax=3D3D4294967295

and forget about it. You'll be fine, and it won't cause you any =3D problems.

-Mark

-----Original Message-----
From: Carmen Rusu [mailto:carmen.rusu_at_rrc.state.tx.us] Sent: Friday, February 13, 2004 9:57 AM
To: mgogala_at_adelphia.net; oracle-l_at_freelists.org Subject: Re: SHMMAX setting with multiple instances? Solaris 2.8,Oracle 8.1.7.4

Here's from Sun Tech support. Does it make any sense to you? To me, it doesnt :-(

> customer. I wouldset=3D20
> shmmax=3D3DTHE_HIGHEST_NUMBER_OF_BYTES_TO_BE_USED_BY_THE_SGA+ some =
extra

> head room.
>=3D20

Carmen Rusu

>>> mgogala_at_adelphia.net 2/13/2004 7:31:05 AM >>>

On 02/13/2004 08:17:14 AM, Carmen Rusu wrote:
> Oracle install guide recommends the minimum value
>=3D20
> set shmsys:shminfo_shmmax=3D3D4294967295
>=3D20
> How does this number depend on the the available physical RAM on the
> box?
>=3D20
> Does this number depend on the number of instances on the box ?
>=3D20
> Did you experiment with this setting? Horror stories?
>=3D20
> Thanks,
>=3D20
> Carmen Rusu
>

Carmen, the number in question is 400MB and it is the maximum size of a shared memory segment on Slowaris. It also represents the largest SGA that oracle can construct in a single piece. It doesn't have any direct impact on your RAM unless you really =3D20 allocate the SGA.

--=3D20
Mladen Gogala
Oracle DBA



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

To unsubscribe send email to: oracle-l-request_at_freelists.org=3D20 put 'unsubscribe' in the subject line.
--
Archives are at http://www.freelists.org/archives/oracle-l/=3D20
FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html=3D20
-----------------------------------------------------------------
----------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
----------------------------------------------------------------
To unsubscribe send email to:  oracle-l-request_at_freelists.org
put 'unsubscribe' in the subject line.
--
Archives are at http://www.freelists.org/archives/oracle-l/
FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html
-----------------------------------------------------------------
----------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
----------------------------------------------------------------
To unsubscribe send email to:  oracle-l-request_at_freelists.org
put 'unsubscribe' in the subject line.
--
Archives are at http://www.freelists.org/archives/oracle-l/
FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html
-----------------------------------------------------------------
----------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
----------------------------------------------------------------
To unsubscribe send email to:  oracle-l-request_at_freelists.org
put 'unsubscribe' in the subject line.
--
Archives are at http://www.freelists.org/archives/oracle-l/
FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html
-----------------------------------------------------------------
Received on Fri Feb 13 2004 - 10:06:07 CST

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US