parallel_adaptive_multi_user

Database env is 9.2.0.6 EE
OS is Tru64 5.1

Does anyone have a formula for how Oracle determines the reduction factor when 
parallel_adaptive_multi_user = TRUE (and obviously parallel_automatic_tuning = 
TRUE)?  I've relied up to this point on using PARALLEL DEFAULT on all objects, 
as our dev, test, and production environments have different CPU counts and I'd 
like relative performance.  But, as the project keeps expanding our servers are 
(fortunately) expanding as well.  Production started with 8 CPUs, now has 10, 
and will shortly be upgraded to 12.  The larger tables aren't growing relative 
to this CPU count.  Instead, we've got new sets of tables and more users, so 
I'd prefer the lower default parallelism of 8.

I'm reluctant to set parallel_adaptive_multi_user = TRUE without first having a 
good idea of how Oracle chooses to reduce the default degree.  Manuals say its 
based on system load and active parallel users.  Great, but is load solely on 
CPU % used or some other resource combination?  For active parallel users, is 
it based on the total of PX slaves across the entire database or just on the 
objects involved?  For both factors, what reduction factor is used?

Thanks.

Dave
-------------------------------------
Dave Herring, DBA
Acxiom Corporation
3333 Finley
Downers Grove, IL 60515
wk: 630.944.4762
<mailto:dherri@xxxxxxxxxx>
-------------------------------------
 
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