[askdba] Re: Question regarding MAX SGA Size and Physical Memory

  • From: "Justin Cave (DDBC)" <jcave@xxxxxxxxxxx>
  • To: <askdba@xxxxxxxxxxxxx>
  • Date: Fri, 29 Oct 2004 12:11:50 -0600

First, I would generally not assign a fixed percentage for executables
and binaries.  Whether you have 1 GB of RAM or 16 GB of RAM, your Oracle
executables and operating system will require the same amount of RAM. =20

Second, since your SGA is so large compared to your PGA, I am hoping
that you are building a pure OLTP application.  Even with that, though,
your PGA is probably a bit on the small side.  If you will be doing any
reporting or you are building a DSS system, your initial estimates are
probably out of whack.

For more discussion on allocating RAM on an Oracle server, there is a
discussion here: http://www.ddbcinc.com/askddbc/topic.asp?TOPIC_ID=3D276

Justin Cave  <jcave@xxxxxxxxxxx>
Distributed Database Consulting, Inc.

-----Original Message-----
From: askdba-bounce@xxxxxxxxxxxxx [mailto:askdba-bounce@xxxxxxxxxxxxx]
On Behalf Of Rajesh Puneyani
Sent: Thursday, October 28, 2004 9:23 AM
To: askdba@xxxxxxxxxxxxx
Subject: [askdba] Re: Question regarding MAX SGA Size and Physical

Hi Yavor,

I was out for a few days hence I could not reply to this.

Thanks for this information. Let me ask another question regarding this
How about following configuration (irrespective of 2Gb limit or 3Gb).
75% to SGA_MAX_Size
15% to PGA
10% Oracle Executables + Binaries etc (like you mentioned)

This way for a 2 Gb limit, we have 200 Mb for EXEs/Binaries and Bad

Do you (or anyone else in this forum) see  any problems with this
configuration ?

Ankur/Ganesh/Others ...Pls. give your expert comments on this ?

Thanks everyone for their contribution.

On Tue, 26 Oct 2004 08:57:15 +0300, Yavor Ivanov <yavor_ivanov@xxxxxxxx>
>        First of all, if you have 4 GB RAM you can easily use 3 GB for
> (Note:1036312.6). In fact, you can use even more with AWE
> but in your case it is not needed.
>        1. If your process space is limited to 2 GB (and it is, if you
do =3D
net set
> the 3 GB switch of Windows), you cannot have 2 GB SGA. Your _whole_
> process space is 2 GB. This is SGA + PGA + Oracle executables and
> libraries (~50 MB). And, in fact, Windows reserves the first and last
64 =3D
> of that 2 GB windows to catch bad pointers. So you never have exact 2
> Remember, the SGA is allocated in granules (16 MB each, in your case),
> you cannot allocate (2GB - 128K)
>        2. No. Note 148495.1 stat=3DD0=3DB5s:
> "At instance startup the Oracle Server allocates the granule entries,
> for each granule to support SGA_MAX_SIZE bytes of address space."
>        So Oracle will try to allocate 2 GB, no matter if you use 128
MB o=3D
r 2 GB
> for all pools.
>        Rgds,
>        Yavor
> On Mon, 25 Oct 2004 17:07:32 -0400, Rajesh Puneyani
> <rajpuneyani@xxxxxxxxx> wrote:
> > Hi guys,
> >
> > We are on windows 2k / oracle 9iR2.
> > One of my database has following configuration -
> >
> > SGA_MAX_SIZE =3D3D 550 Mb
> > SIZE of SGA =3D3D 550 Mb
> >
> > This has to be a dedicated database on this server (with 4Gb RAM).
> > whole 2Gb can be dedicated to this one database.
> >
> > 1. Now If I shutdown this database, change the parameter
> > =3D3D 2Gb then can I expect any issues while restarting the database =
> >
> > 2. If LOCK_SGA is false then Step 1 would not have any effect on
> > ACTUAL SGA Size..Right ? Pls. confirm.
> >
> > Your insight on this would be highly appreciated.
> >
> > Thanks and Regards
> > Rajesh
> >
> >
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