parallel_adaptive_multi

From: Herring Dave - dherri <Dave.Herring_at_acxiom.com>
Date: Wed, 24 Jan 2007 14:17:14 -0600
Message-ID: <7ED53A68952D3B4C9540B4EFA5C76E3602BC770D@CWYMSX04.Corp.Acxiom.net>

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_at_acxiom.com>

"When I come home from work and see those little noses pressed against the windowpane, then I know I am a success" - Paul Faulkner

The information contained in this communication is confidential, is intended only for the use of the recipient named above, and may be legally privileged.

If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited.

If you have received this communication in error, please resend this communication to the sender and delete the original message or any copy of it from your computer system.

Thank You.

--
http://www.freelists.org/webpage/oracle-l

Received on Wed Jan 24 2007 - 14:17:14 CST