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Home -> Community -> Mailing Lists -> Oracle-L -> Re: oica/oic
db file sequential read comes from single block reads, which tend to be indexed accesses anyway.
Both these parameters make the optimizer reduce the "calculated cost" of a single block reads - not the "actual resource requirement" - which tends to favour indexed accesses over tablescans, and can favour bad indexes over good indexes.
Consequently, if you are already seeing a lot of db file sequential reads, fiddling with these parameters is not very likely to help.
Your best bet is to examine sessions (such as your batch job) which are exhibiting excessive wait time on these reads, then focus on the SQL that is used by those sessions to figure out why particular statements are doing excessive amounts of reads. Once you know what the problem is, you have a better chance of picking an appropriate solution.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
April 2004 Iceland http://www.index.is/oracleday.php June 2004 UK - Optimising Oracle Seminar July 2004 USA West Coast, Optimising Oracle Seminar August 2004 Charlotte NC, Optimising Oracle Seminar September 2004 USA East Coast, Optimising Oracle Seminar September2004 UK - Optimising Oracle Seminar
Thankyou Jonathan! I read that document, I don't know exactly what Iam = missing!! But last two months Iam checking my db with lots of db file = sequential reads(90%) in my statspack, so lots of single block reads and = multiblock reads with nested loops. Most of my erp tables had indexes = with stats. So optimizer has same info to make better decision??
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