Re: Deadly OPTIMIZER_SECURE_VIEW_MERGING=TRUE

On Dec 2, 12:30 pm, Rick Denoire <educacion.super..._at_online.de> wrote:

> Can you confirm that reverting mentioned parameter to the non-default
> value (FALSE) improves performance so dramatically?

in some cases it might, depends on what the views are like in your application.
If it works, then use it!

> What is the rationale of such detrimental default value of the
> initalization parameter that effectively renders the database
> "misconfigured"?

not really. it's very dependent on the type of views and the application itself. I've seen this not take any effect whatsoever and I've seen it make a huge difference. Go figure...

> Are there any other deadly preset parameters I should be aware of
> after Upgrade to Oracle 10g, according to your experience?

_unnest_subquery=true (default)

even in 10.2.0.3 patched, I'm still getting a lot of complex Peoplesoft queries with problems with this one, particularly with the ubiquitous (select max(date_field) ...)
subqueries of this product. Set it to false and problems vanish.

> Do you really recommend to let Oracle do things automatically? (SGA,
> PGA, db_file_multibloc_read_count, etc.)

if you don't have multiple schemas then it's fine. If you do, then watch out for tables with the same name in different schemas and auto sga: deadly combination! Received on Sun Dec 02 2007 - 06:23:11 CST