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Home -> Community -> Mailing Lists -> Oracle-L -> RE: 9i - Dynamic SGA - SGA_MAX_SIZE
Mladen,
But then again, shmget and shmat use malloc/calloc internally, it just
differs in that shmget/shmat create the memory space and then make a "public
handle" so that multiple processes can access the memory allocated. (Very
simplisticly put)
So in a certain sense it is more than just a similar mechanism.
What was this discussion about anyway ;)
-----Mensaje original-----
De: Mladen Gogala [mailto:mladen_at_wangtrading.com]
Enviado el: viernes, 08 de agosto de 2003 16:09
Para: Multiple recipients of list ORACLE-L
Asunto: RE: 9i - Dynamic SGA - SGA_MAX_SIZE
BTW, my debate of this issue was completely incorrect. As a colleague from
This list has noted, SGA is created using shmget and shmat, not malloc and
calloc.
The only explanation might be that the mechanism is similar to the one of
malloc.
-- Mladen Gogala Oracle DBA -----Original Message----- Jessica Mao Sent: Tuesday, August 05, 2003 6:34 PM To: Multiple recipients of list ORACLE-L don't know if it's still true, i played with sga_max_size and db_cache_size a year ago on 9.0 & Solaris8 & F15k w/o much luck. when sga_max_size = 64G and db_cache_size = 32G, db started impressingly fast. but db server cpu sys% jumped up to 90+ during warming-up tests, leaving usr% close to 0. tests never finished. reduced sga_max_size = 40G and db_cache_size = 32G, db cpu still around 50% sys. sga_max_size = 18G and db_cache_size = 16G, db performing ok. after that gave up sga_max_size, increased db_cache_size to 24G (sga_max_size was then auto set to 24G). db performing ok. db_cache_size = 32G (= sga_max_size). took 32 min to start db. db performing ok. db_cache_size = 40G (just curious), took 40min to start db. db performing ok. -Jessica --- Mohammed Shakir <mshakir08816_at_yahoo.com> wrote:Received on Fri Aug 08 2003 - 15:39:27 CDT
> Kirti
>
> Thanks for the info.
>
> I could not raise dynamically the size of db_cache_size and did not
> know why, until I noticed the new parameter sga_max_size. Anyway, I
> tried to lower the size of db_cache_size dynamically and I did not
> have a problem. So sgma_max_size does play its role in
> db_cache_sizing.
>
> I have not tested where I increase the size of sga_max_size using
> init.ora and then try to increase the size of db_cache_size
> dynamically by the same size as the increase in sga_max_size. That is
> the test for coming weekend.
>
>
> --- Kirtikumar Deshpande <kirtikumar_deshpande_at_yahoo.com> wrote:
> > SGA_MAX_SIZE was introduced in 9i to allow dynamic sizing of SGA
> > (Dynamic Sizing feature) components such as, shared pool, large
> > pool, buffer cache etc. In versions up to 8i, such changes
> > required bouncing the instance.
> > This parameter assumes the value of the SGA at instance startup.
> > Various components of the SGA can
> > then be increased/reduced as and when needed. The total SGA, thus,
> > can reach a maximum value set
> > by SGA_MAX_SIZE (if set in the init.ora file). That's the idea.
> > However, the implementation is
> > different on various platforms. With ISM, and DISM, on Solaris, there
> > are other issues when it
> > comes to using Dynamic SGA. You may want to search Metalink for
> > specific notes/articles for
> > Solaris.
> > On AIX 5L as I found out, Oracle uses SGA_MAX_SIZE, if set in
> > init.ora, at the instanace startup,
> > and allocates the excess (difference in computed SGA value and set
> > SGA_MAX_SIZE) to 'variable
> > size'. Hence there is no room for any dynamic sizing (upward) of any
> > SGA component. I did not try
> > to downsize shared pool first, and 'upsize' buffer cache later. May
> > be that would work, but that
> > is not the intention of using this parameter.
> >
> > PGA_AGRREGATE_TARGET is completely different from this parameter. It
> > sets an instance-wide upper limit for the memory used by sorting,
> > hashing processes.
> >
> > Hope this helps..
> >
> > - Kirti
> >
> >
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No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. Wang Trading LLC and any of its subsidiaries each reserve the right to monitor all e-mail communications through its networks. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorized to state them to be the views of any such entity. --------------------------------------------------------- -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mladen Gogala INET: mladen_at_wangtrading.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jessica Mao INET: jmao_at_portal.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -------------------------------------------------------- Note: This message is for the named person's use only. It may contain confidential, proprietary or legally privileged information. No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. Wang Trading LLC and any of its subsidiaries each reserve the right to monitor all e-mail communications through its networks. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorized to state them to be the views of any such entity. --------------------------------------------------------- -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mladen Gogala INET: mladen_at_wangtrading.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Nelson Flores INET: nflores_at_intec.cl Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
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