Is the problem the Optimizer or something else? Have you confirmed that the CBO is using different execution plans for the same statement? If the plans are the same, but the execution time is not, your problem is elsewhere. Your read operations could be taking more time, sorts/memory joins could be slower, etc. Daniel Fink ---------------------------------------------------------------- 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 -----------------------------------------------------------------