I believe that you would need to increase the buffer cache size to compensate OS file cache vanished by direct I/O. ================================ Dion Cho - Oracle Performance Storyteller http://dioncho.wordpress.com (english) http://ukja.tistory.com (korean) http://sites.google.com/site/otpack (tpack) ================================ 2010/11/28 Mohammad Rafiq <rafiq9857@xxxxxxxxxxx> > You did not mention oracle version. Try to get it set aio-max-nr to > 1048576 (default is 65536). If it is 10.2.0.5 then it must be 1048576 as a > work around. > > Regards > Rafiq > > > From: jcmiranda@xxxxxxxxx > > > To: przemolicc@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx > > Date: Fri, 26 Nov 2010 12:58:22 +0100 > > Subject: RE: direct IO > > > > > > > We are getting > > > > WARNING:io_submit failed due to kernel limitations MAXAIO for process=128 > pending aio=110 > > WARNING:asynch I/O kernel limits is set at AIO-MAX-NR=3145728 > AIO-NR=77074 > > WARNING:Oracle process running out of OS kernel I/O resources (1) > > WARNING:Oracle process running out of OS kernel I/O resources (1) > > WARNING:Oracle process running out of OS kernel I/O resources (1) > > > > on several systems with linux pppc64 and it seems there are no patch for > this error on this platform. > > I can´t tell if direct i/o is slower. > > > > Anyone know how to solve this problem? > > > > ________________________________________ > > De: oracle-l-bounce@xxxxxxxxxxxxx [oracle-l-bounce@xxxxxxxxxxxxx] En > nombre de przemolicc@xxxxxxxxx [przemolicc@xxxxxxxxx] > > Enviado el: viernes, 26 de noviembre de 2010 10:21 > > Para: oracle-l@xxxxxxxxxxxxx > > Asunto: Re: direct IO > > > > On Thu, Nov 25, 2010 at 05:32:02PM +0200, Laimutis.Nedzinskas@xxxxxxxxxxx: > > > Looking for experiences/advices of others regarding one issue with > direct > > > IO. > > > > > > Recently we switched to another data center and some databases reported > > > increased IO time. > > > After investigating we found that IO is slower on file systems > (Veritas, > > > Solaris 10) mounted with direct io options. > > > AWR shows more time on scattered reads but for the same number of > blocks > > > too. > > > We are going to switch of direct IO and test but for the time beeing I > am > > > wandering why direct IO is bad in our case. > > > > > > We've got seriously increased times for statistics gathering which does > > > full scan naturally - we've found 2 full scan sqls on the same table > > > clearly comming from dbms_stats package . Full scan is not cached by > > > oracle. But file system cache can help in that particular case. > > > > Do you have exactly the same storage configuration in both data centers ? > > > > We found that _usually_ switching from buffered filesystem to direct IO > won't > > help unless you increase also Oracle buffers (so Oracle uses memory which > > had been used previously for filesystem buffering). > > Also on Veritas/UFS I recommend to turn on direct IO in Oracle > (FILESYSTEMIO_OPTIONS=SETALL) > > and not in Veritas (we don't set any mount options in /etc/vfstab for > Veritas filesystems). > > > > If you bought Veritas ODM - just use it. > > > > Regards > > Przemyslaw Bak (przemol) > > -- > > http://przemol.blogspot.com/ > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ---------------------------------------------------------------------- > > Najlepsza wyszukiwarka tanich lotĂłw! > > SprawdĹź >>> http://linkint.pl/f284a > > > > -- > > //www.freelists.org/webpage/oracle-l-- > > //www.freelists.org/webpage/oracle-l > > > > >