Note in line. 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 March 2004 Hotsos Symposium - The Burden of Proof Dynamic Sampling - an investigation March 2004 Charlotte OUG (www.cltoug.org) CBO Tutorial April 2004 Iceland June 2004 UK - Optimising Oracle Seminar ----- Original Message ----- From: "Joze Senegacnik" <JozeS@xxxxxxxxxxxxxx> : According to the Metalink note you can even achieve 8.1.7 behavior when you : set MREADTIM = 1.2 * SREADTIM and MBRC=8, but I haven't tested this. And : finally I haven't heard for a negative feedback till now and this counts as : well. But as usual happens in real life also the system stats is not solving : all problems. : My guess is that this was an observation taken from an experiment. It's close to true if the parameter db_file_multiblock_read_count that is used as the comparison was set to 8. The time factor has to change if the two MBRCs are set to a different value. The old costing model would adjust 8 to 6.59 (working from memory here) before dividing into the table's number of blocks below HWM. Surprise, surprise: 6.59 * 1.2 = 7.9. Why does it work - because, as the formula in the manual points out, Oracle effectively treats a multiblock read cost as mreadtim/sreadtim * single block read cost. There will be a little inaccuracy, though, because of the "plus 1" that oracle adds to tablescans in 9. ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------