Message-ID: <F001.005C8783.20030802095923@fatcity.com>
Date: Sat, 02 Aug 2003 09:59:23 -0800
To: Multiple recipients of list ORACLE-L <ORACLE-L@fatcity.com>
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From: Mohammed Shakir <mshakir08816@yahoo.com>
Subject: RE: 9i - Dynamic SGA - SGA_MAX_SIZE
Organization: Fat City Network Services, San Diego, California
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I am little confused about this issue to. I am working on Oracle
9.2.0.3 on Solaris 9 (64 bits) platform. I did not set sga_max_size
parameter and I see it set. I am not sure what it means and what kind
of problem it will cause me. 

I have pga_aggregate_target is set for 512MB and it seems it is not
counted in this count. I know it is a separate space in the memory.
Since this is a new system for me, I am little concerned that Oracle
does not chock on me.

--- Kirtikumar Deshpande <kirtikumar_deshpande@yahoo.com> wrote:
> It does not work as advertised, in AIX either... I played with this
> in AIX 5L. 
> 
> 
> - Kirti 
> 
> 
> --- "Hately, Mike (LogicaCMG)" <mike.hately@nedl.co.uk> wrote:
> > Stephen,
> > 
> > The documentation is pretty wooly regarding this issue but the way
> it seems
> > to be intended to work is this:
> > At startup Oracle will allocate an SGA sized as specified in the
> > sga_max_size parameter. This is to ensure that the system has
> enough memory
> > accomodate what you see as a maximum requirement for the SGA.
> > After it's allocated this and started the database it should
> deallocate any
> > memory it holds over and above that required to store the
> components of the
> > SGA. In some platforms/versions this deallocation doesn't occur.
> Solaris for
> > example behaves like this unless you move to version 8. 
> > It's possible that your version of Tru64 has a similar limitation
> or that
> > you're seeing a bug. 
> > To my mind though, Oracle Support's claim that this is expected
> behaviour is
> > a bit of a cop out. This is certainly not the way it was supposed
> to work.
> > The concept guide states the following:
> > 
> > "The SGA can grow in response to a database administrator
> statement, up to
> > an operating system specified maximum and the SGA_MAX_SIZE
> specification."
> > 
> > and 
> > 
> > "Oracle can start instances underconfigured and allow the instance
> to use
> > more memory by growing the SGA components, up to a maximum of
> SGA_MAX_SIZE"
> > 
> > Both of these statements imply that the unused memory is supposed
> to be
> > released back to the operating system.
> > The way that this feature operates on your system it allows you to
> juggle
> > storage backwards and forwards between caches which is still useful
> but not
> > 'what it says on the box'.
> > 
> > I'd ask Oracle under what cirtcumstances this is normal behaviour.
> It's not
> > the way the software is intended to work so maybe it's a platform
> > limitation. 
> > 
> > In order to give you a better idea of what Oracle thinks it's SGA
> is using
> > you can query the following views :
> > 
> >  - V$SGA_CURRENT_RESIZE_OPS: 
> >    Information about SGA resize operations that are currently in
> progress. 
> >    An operation can be a grow or a shrink of a dynamic SGA
> component.
> >  
> >  - V$SGA_RESIZE_OPS: 
> >    Information about the last 100 completed SGA resize operations. 
> >    This does not include any operations currently in progress. 
> > 
> >  - V$SGA_DYNAMIC_COMPONENTS: Information about the dynamic
> components in
> > SGA. 
> >    This view summarizes information based on all completed SGA
> resize
> > operations since startup. 
> > 
> >  - V$SGA_DYNAMIC_FREE_MEMORY: 
> >    Information about the amount of SGA memory available for future
> dynamic
> > SGA resize operations. 
> > 
> > 
> > Hope this helps,
> > Mike Hately
> > 
> > 
> 
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> Author: Kirtikumar Deshpande
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=====
Mohammed Shakir
CompuSoft, Inc.
11 Heather Way
East Brunswick, NJ 08816-2825
(732) 672-0464 (Cell)
(732) 257-6001 (Home)

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