Re: Telling When Statistics Present

In <46gp7g$3tn_at_lastactionhero.rs.itd.umich.edu>, Dave McLaughlin <davemc_at_umich.edu> writes:
>We are running RDBMS 7.1.4 on AIX and Server Manager 2.0.4 on Windows.
>
>We just upgraded the server from 7.0, and I made what appears to be a
>startling discovery. We have specified optimization_mode "choose" in
>init.ora, and we believed that we were using the rule-based optimizer
>most of the time. However, over half of our tables have statisitics
>present according to Server Manager (the "optimizer" tab in the "schema"
>file). We have no idea how this could be. Could Server Manager be
>wrong? Are there any likely ways of generating object statistics other
>than explicit use of the ANALYZE command? Are we really using the
>cost-based optimizer with these tables?
>
>TIA
>
>Dave McLaughlin
>University of Michigan
>

Dave, We are using the cost-based optimizer successfully. Under version 7.1.4 we had to use a lot of hints to have it choose the right plan but when we upgraded to version 7.1.6 most of them could be removed. With the installation of 7.2 we were able to remove hints completely and have statistics run on all tables. Version 7.2 has a very much improved optimizer. Some plans even choose full-table scan over index with much success. Each version gets better. I have heard someone state that version 7.3 will have a heuristic approach where it will learn from history what plan to use.

scott moyer
dmoyer_at_gpu.com (work)
dsmoyer_at_enter.net (home) Received on Wed Oct 25 1995 - 00:00:00 CET