AFAIK it depends on OS, in Linux for example by default it tries to cache everything (you can tweak some kernel parameters), in HP-UX its determined by dbc_max_pct kernel parameters. Solaris you need to google :-( Your test would be using SAME SGA, create a table in a Filesystem without DIO and create same table in another filesystem with DIO. Preferably one tablespace per table. Flush buffer cache to ensure nothing is cached, run FTS on first table 3 or 4 times, flush buffer cache again and repeat the FTS with second table. If you cannot afford flush the whole buffer cache then take the tablespaces offline and online would do. Thanks -- LSC On Nov 21, 2007 12:37 PM, DBA Deepak <oracle.tutorials@xxxxxxxxx> wrote: > Thanks LS for your pointer. But have one question. Is the file system > buffer big enough to cache large table's data, so that FTS of large > tables will be faster? > > How to know how big is the file system's cache? > > Deepak > > > > On Nov 21, 2007 4:45 PM, LS Cheng <exriscer@xxxxxxxxx> wrote: > > Hi > > > > I shall point you to a ML note 462072.1 which talks about Linux but the > > theory applies for other UNIX flavours as well. > > > > I had recent experience with DIO in AIX, the database actually went > worse > > when DIO was enabled it was because the application did many full table > > scans even though I doubled buffer cache. > > > > Thanks > > > > -- > > LSC > > > > > > > > > > > > On Nov 21, 2007 12:01 PM, DBA Deepak <oracle.tutorials@xxxxxxxxx> wrote: > > > Hi LS, > > > > > > Can you please help me in understanding how direct i/o will make the > > > FTS of a big table slower? > > > > > > If FTS becomes slow then is it not recommended to use directio where > > > FTS of large tables are done? > > > > > > As per many experts we should always use directio+ufs combination for > > > oracle files related disks. > > > > > > Deepak > > > > > > > > > > > > > > > On Nov 21, 2007 4:08 PM, LS Cheng < exriscer@xxxxxxxxx> wrote: > > > > one option is brute force :-P > > > > > > > > create a very big table and full scan it, direct i/o will be slower > > because > > > > filesystem buffer would help in this case! > > > > > > > > -- > > > > LSC > > > > > > > > > > > > > > > > > > > > On Nov 21, 2007 10:11 AM, DBA Deepak < oracle.tutorials@xxxxxxxxx> > > wrote: > > > > > > > > > > > > > > > > > > > > Hi John, > > > > > > > > > > Sorry for the late response. Even after mounting the filesystem > with > > > > > "forcedirectio" option am unable to see a non-zero value as the > third > > > > > parameter value to the ioctl() calls. I did the same experiment as > > > > > mentioned in your previous mail. > > > > > > > > > > Would you please tell is there any alternative to verify whether > the > > > > > system is using directio or not? > > > > > > > > > > Regards, > > > > > > > > > > Deepak > > > > > > > > > > > > > > > > > > > > > > > > > On Oct 18, 2007 12:45 PM, John Hallas < john.hallas@xxxxxxxxxx> > wrote: > > > > > > > > > > > > > > > > > > > > > > > > Have the filesystems been mounted with direct_io option? > > > > > > > > > > > > > > > > > > ________________________________ > > > > > > > > > > > > > > > > > > From: oracle-l-bounce@xxxxxxxxxxxxx > > > > [mailto:oracle-l-bounce@xxxxxxxxxxxxx ] > > > > > > On Behalf Of DBA Deepak > > > > > > Sent: 17 October 2007 19:39 > > > > > > To: John Hallas > > > > > > Cc: oracle-l > > > > > > Subject: Re: filesystemio_options option on solaris 9 sparc > 64-bit > > > > (Oracle > > > > > > 10g) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi John, > > > > > > > > > > > > > > > > > > > > > > > > Thanks for your help. In my environment filesystemio_options is > set > > to > > > > > > SETALL > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Still it is not using directIO as per your test. My server is > sparc > > > > Solaris > > > > > > 9, 64 bit with Oracle 10.2.0.3. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Can you please help me in troubleshooting the same. Am I missing > > > > anything? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ________________________________ > > > > > > > > > > > > BJSS Limited, 1st Floor Coronet House, Queen Street, Leeds LS1 > 2TW. > > > > > > Registered in England with company number 2777575. > > > > > > http://www.bjss.co.uk > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > Regards, > > > > > > > > > > Deepak > > > > > Oracle DBA > > > > > -- > > > > > //www.freelists.org/webpage/oracle-l > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > Regards, > > > > > > Deepak > > > Oracle DBA > > > > > > > > > > > -- > Regards, > > Deepak > Oracle DBA >