On 05/19/2005 10:41:24 PM, Larry Elkins wrote: > Wolfgang and others, >=20 > Assuming 9i or higher, and work area size policy of auto and pga aggregat= e > target set, could this cause a plan change depending upon the workload on > the machine?=20 Larry, according to what I know, the statement plan depends entirely on the= statistics (with histograms, of course) and availability of usable indexes. That is th= e working=20 hypothesis and I haven't yet found any evidence to the contrary, not even i= n version 10g. The only way I can envision that Oracle is going to change the plan, depend= ing on the machine utilization is by changing the statistics, depending on the machine utiliza= tion. That=20 narrows things down to dynamic sampling. Dynamic sampling does not collect = system statistics, as far as I know. The only way to do what you say would be for CBO to dynam= ically sample=20 system statistics and change CPUSPEED. I am not aware of any situation in w= hich optimizer would do so. In addition to that, applications are often based on the parti= cular execution plan for the critical statements. Having a feature like that would result in hav= ing applications behaving unpredictably. I honestly do not see that happening. --=20 Mladen Gogala Oracle DBA -- //www.freelists.org/webpage/oracle-l