Wolfgang is right, I read that from Tom Kyte, You can use system statistics or the parameters I think that was on his book about design. The point is I'm not going to start to experiment on customers database, and this is not a 30 minutes test to do in my free time. So I can't apply statistics without experiment on customer test database previously, and I can't expriment on test customer database preveiously, without my boss permission. So when the time will come I'll see. :) -- //www.freelists.org/webpage/oracle-l