Re: RULE vs. COST OPTIMIZATION & STATIS

Jeff K <102172.2033_at_CompuServe.COM> wrote:
>1. Does the collection of statistics impact rule based optimization ?

Strictly speaking no. but the existance of statistics may determine IF you are using RBO at all.

>2. Does the collection of statistics cause an outage to the
>tables involved; couldnt concurrent read happen ?

I cant confirm it right now but since I had problems in a ReadOnly appl during collection I'm pretty sure analyze table gets an exclusive lock.

>3. Is it true that a single SQL statement can use both rule and
>cost based optimization ??

You can run a statement once using the RBO and then again using the CBO as long as you have done the things you need to do to make sure a differnt optimizer is used. ie) HINTS

-- 
Regards, 

Lee E. Parsons                  		
Systems Oracle DBA	 			lparsons_at_world.std.com