One relatively effective way to convert an app from rule to cost is to enable cost in a very "rule-oriented" way (namely, you want indexes to be chosen almost religiously).
You enable cbo but set things like optimizer_index_cost_adj and optimizer_index_caching to very index favourable values. I remember when SAP went to rule to "cost" and whilst I'm sure some code changes took place I also remember setting the adjust parameter to '10' (instead of 100) so nested loop access was still the dominant access path. Of course, this all needs testing and your good friends at Siebel would probably not support you - but I've seen it used very successfully a number of times in the past because you get "rule-like" access paths but all the goodies that go with cbo as well. hth connor --- Michael Fontana <[EMAIL PROTECTED]> wrote: > > > I would like to ask a question of this esteemed and > knowledgeable audience > about running > SIEBEL applications on Oracle. Siebel insists that > their CRM application > will only run with > acceptable performance if rule-based optimization is > chosen, yet, as we all > know, there are > documented examples of poor performance, and strong > recommendations to the > contrary from Oracle. > > At one point, I recall reading an article from a > knowledgeable consultant > describing what must be done > to get Siebel to run with optimizer_mode=choose. > Any assistance in > reaching this goal, or comments, > would be more than appreciated. We're still in the > implementation phase, > and are already receiving > poor performance on certain processes, even using > the recommended rule > based optimization. I > predict it will only get worse! > > > ===== Connor McDonald web: http://www.oracledba.co.uk web: http://www.oaktable.net email: [EMAIL PROTECTED] "GIVE a man a fish and he will eat for a day. But TEACH him how to fish, and...he will sit in a boat and drink beer all day" __________________________________________________ Do You Yahoo!? Everything you'll ever need on one web page from News and Sport to Email and Music Charts http://uk.my.yahoo.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: =?iso-8859-1?q?Connor=20McDonald?= INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- 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).
