Re: Should we stop analyzing?

• Original Message -----

> The issue here is that very few people understand how the CBO
> works, or what the statistics do, or how to use them properly.

And a seriously *big* component of that problem is that Oracle keeps changing/patching/modifying the CBO and how it reacts to certain combinations of information, on EVERY SINGLE point version! It's virtually impossible for a typical DBA to find the time to fully test all the combinations and find out what works where and how. Hence why this type of thread becomes so useful.

> Do they clone the production database, change the statistics, prove that the
> system can complete it's batch job in 8 hours, then install ? I doubt it.

Exactly my point above. Not feasible. So, what's the alternative given that:

1- the information in Oracle's own doco is far from complete or covering all bases?

2- the CBO like any other piece of code, is sometimes buggy?

3- You, Don, SA, and so many others who have the time to investigate this may in turn not have the time to produce the detailed doco that is needed to understand how the CBO works in all situations?

Is dynamic sampling the solution? I don't think so: if anything, it will enhance/increase the problems caused by 1 and 2.

> approach, while the 10g developers are pissed that the CBO has been getting
> a bum-rap because of crappy statistics.

<cough>itwouldhavehelpediftheyhadfixedthecodebackin7/8/9insteadofdelivering aseriesofpatchesasnewreleasesthattotallyconfusedeverybodyaboutitsoperation<cough>

Cheers
Nuno Souto
nsouto_at_optusnet.com.au

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Author: Nuno Souto
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