It's interesting that you should have heard that. My first interpretation of the optimizer_index_cost_adj was that it was an estimate of the table logical I/O that would become physical I/O (and ignore the fact that this was allowed to go above 100%) - which brings it into line, somewhat, with the optimizer_index_caching in terms of 'addressing the same issue'.
However, I decided that your interpretation was a much nicer, more intuitive, way of appreciating the significance of the number and deciding on a rational setting for it. But I'm inclined to agree with you - even if they were supposed to be addressing the same problem in different ways, they do seem to be jointly and separately (as the lawyers say) viable. Have you tried any experiments yet which mix dbms_stats.system_stats figures with the effects of these two parameters ? That ought to be a case of when we should do one or the other. Jonathan Lewis http://www.jlcomp.demon.co.uk Author of: Practical Oracle 8i: Building Efficient Databases Next Seminar - Australia - July/August http://www.jlcomp.demon.co.uk/seminar.html Host to The Co-Operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html -----Original Message----- At IOUG-A, I heard discussion that the OPTIMIZER_INDEX_CACHING and OPTIMIZER_INDEX_COST_ADJ were two separate approaches developed by different development teams within Oracle that had the exact same purpose. So, the argument was advanced that setting *either* one *or* the other was sufficient, but not *both*. Not having any access to the internal goings-on in Oracle ST Development, I'm sticking with the idea that these two parameters are addressing *different* and very specific issues, so they both should be considered and used independently of one another... I have a paper on this topic at http://www.EvDBT.com/SearchIntelligenceCBO.doc that discusses these issues in more depth... -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Jonathan Lewis INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- 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). You may also send the HELP command for other information (like subscribing).
