Monday Oct 08, 2012

OOW 2012:
Slides Download

Hm ... you might ask yourself why there are no Oracle Database 12c slides available for download, neither in the OOW 2012 content system nor on our blog (and I believe nowhere else).

Simple reason: As long as Oracle Database 12c is not released and available we are not allowed to offer slides for download. Therefore people were simply taking pictures during the 12c sessions with their phones, iPods and cameras. Roy took a nice shot:


Sorry for that - we'll make the content available as soon as Oracle Database 12c gets released.

In between you can download our OOW 2012 talk Database Upgrades on Steroids: Real Speed, Real Customers, Real Secrets as PDF (3.4MB) - but the 12c content is currently not in that PDF. But a lot of information applies to your source database and/or to any upgrade - so it still might be helpful. And unfortunately the same 12c rule applies to the slides guiding you through our Hands-On-Lab on Tuesday.

Thanks :-)

Tuesday Apr 03, 2012

New Slides - and a discussion about Dictionary Statistics

First of all we have just upoaded a new version of the Upgrade and Migration Workshop slides with some added information. So please feel free to download them from here.The slides have one new interesting information which lead to a discussion I've had in the past days with a very large customer regarding their upgrades - and internally on the mailing list targeting an EBS database upgrade from Oracle 10.2 to Oracle 11.2.

Why are we creating dictionary statistics during upgrade?

I'd believe this forced dictionary statistics creation got introduced with the desupport of the Rule Based Optimizer in Oracle 10g. The goal: as RBO is not supported anymore we have to make sure that the data dictionary has fresh and non-stale statistics. Actually that would have led in Oracle 9i to strange behaviour in some databases - so in Oracle 9i this was strongly disrecommended.

The upgrade scripts got hardcoded to create these stats. But during tests we had the following findings:

It's important to create dictionary statistics the night before the upgrade. Not two weeks before, not 60 minutes before your downtime begins. But very close to the upgrade. From Oracle 10g onwards you'd just say:

$ execute DBMS_STATS.GATHER_DICTIONARY_STATS;

This is important to make sure you have fresh dictionary statistics during upgrade for performance reasons. Tests have shown that running an upgrade without valid dictionary statistics might slow down the whole upgrade by factors of 2x-3x.

And it would be also a great idea post upgrade to create again fresh dictionary statistics when you've did suppress the stats creation during the upgrade process. Suppress? Yes, you could set this underscore parameter in the init.ora:

_optim_dict_stats_at_db_cr_upg=FALSE

to suppress the forced dictionary statistics collection during an upgrade. We believe strongly that (a) people using the default statistics creation process which will create dictionary statistics by default and (b) create fresh stats before upgrade on the dictionary. Therefore we find it save once you have followed our advice to use the underscore during upgrade. And we've taken out that forced statistics collection during upgrade in the next release of the database.

Please note: If you are using the DBUA for the upgrade it will remove underscore parameters for the upgrade run to improve performance - which is generally a good idea. So you'll have to start the DBUA with that call:

$ dbua -initParam "_optim_dict_stats_at_cb_cr_upg"=FALSE

-Mike

Thursday Nov 17, 2011

DOAG Conference 2011: Seven Flavors of Database Upgrades

Thanks to everybody who did attend at my DOAG Conference session in N├╝rnberg this year "Seven Flavor of Database Upgrades" (or in German: "7 Wege zum Datenbank-Upgrade - Geschichten, die das Leben schrieb"). And thanks for your patience staying with me in overtime as well ;-)

In case you'd like to download the slides I've presented at the session please download them via this link or from the download section to your right.

About

Mike Dietrich - Oracle Mike Dietrich
Senior Principal Technologist - Database Upgrade Development Group - Oracle Corporation

Based near Munich/Germany and spending plenty of time in airplanes to run either upgrade workshops or work onsite with reference customers. Acting as interlink between customers and the Upgrade Development.

Contact me either via XING or LinkedIn

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