Each new release of Oracle brings enhancements, and 10g has radically changed some important defaults for Oracle statistics collection (using dbms_stats). The one-size-fits-all approach is a great baseline, but the automatic 10g statistics collection may not be just-right for your database.
Oracle 10g does automatic statistics collection and your original customized dbms_stats job (with your customized parameters) will be overlaid.
You may also see a statistics deficiency (i.e. not enough histograms) causing performance issues. Re-analyze object statistics using dbms_stats and make sure that you collect system statistics.
execute dbms_stats.gather_system_stats('start');
-- wait an hour or so
execute dbms_stats.gather_system_stats('stop');
With Oracle Database 10g, there are some new arguments available for the dbms_stats package subprograms. Those changed 10g dbms_stats parameters are granularity and degree.
There are also cases where you need to disable the automatic statistics collection on Oracle10g.
Read more about importatnt changes in 10g statistics collection here:
http://oracle-tips.c.topica.com/maalOG5abHNJ0bLGJrib/
Important Changes in 10g Statistics Collection
