Why I have db_cache_size set to zero in my database? SQL> show parameter db_cache_size
NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ db_cache_size big integer 0 SQL> -----Original Message----- Sent: Tuesday, August 05, 2003 5:34 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 <[EMAIL PROTECTED]> wrote: > 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 <[EMAIL PROTECTED]> 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 > > > > __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Kirtikumar Deshpande INET: [EMAIL PROTECTED] 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: [EMAIL PROTECTED] (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). 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