Wednesday May 02, 2012

Behaviour Changes Oracle 8i to 11.2 + New Features Oracle 11.2 + refreshed Upgrade and Migration Slides

We have uploaded refreshed and new slide sets:

Wednesday Feb 15, 2012

Why is every patchset now a full release?

This question got posted by Naveen in the previous entry today - and I found it worth it to create a new blog entry as this question gets raised in nearly every 2nd workshop as well - so others might be interested as well.

Mike,

A question has been bothering me for a while and I thought I'll throw it out there. I didn't raise a support ticket, I knew what the response is going to be.

So here is the question. I have an 11g ORACLE HOME that was built as 11.2.0.1. Now if I want to upgrade to 11.2.0.2 or 11.2.0.3, I guess there is no easy way to upgrade the existing ORACLE HOME. Why didn't Oracle give the option to just apply a patch (opatch) and upgrade to 11.2.0.2 (or .3). For a customer to create a new ORACLE HOME is just a lot of work and breaks a lot of things. We have to copy over so many configs from the old home to the new home.

I'm sure there is a good reason, I'm just trying to understand what they are.

Thanks
Naveen

Naveen, thanks for your question. And the answer has many aspects.

Install into your existing ORACLE Home

First of all you can still install the new patch set (which is now a full release since Oracle 11.2.0.2) into your existing $ORACLE_HOME. But you'll have to detach your current home from the OUI's inventory first. Please see slide 41 of the Upgrade and Migration workshop deck. Please backup the contents of $ORACLE_HOME/dbs and $ORACLE_HOME/network/admin first as you'll have to copy them back later.

$ ./runInstaller -detachHome ORACLE_HOME=/u01/orahomes/11.2.0

Starting Oracle Universal Installer...

Checking swap space: must be greater than 500 MB. Actual 10047 MB Passed

The inventory pointer is located at /etc/oraInst.loc

The inventory is located at /u01/orabase

'DetachHome' was successful.

Once you've done that you'll install into your existing (old) directory.  And finally you'll copy back your dbs and network/admin files.

Why customers might use this procedure?

There are basically two reason why a customer chooses this strategy:
(a) Home naming conventions not allowing an Oracle 11.2.0.2 home and another Oracle 11.2.0.3 home
(b) Space issues
Both are valid reasons and therefore you can stay with the old strategy.

Why did we change from patchsets to full release patchsets?

Simple reason: Customers did ask us for a looooong time why we are delivering 3GB large patchsets instead of full releases. So we'd follow this wish. And second it will decrease the overall downtime when you'd install into your new Oracle Home. If you apply patchset software to your existing Oracle Home every Oracle process serviced by that home must be shut down as well - obviously including the database(s). And furthermore if something fails you'll have to restore your OUI's inventory plus all home contents - or reinstall your previous Oracle software.

Besides that we recommend to patch this home first with important one-offs (see links in MOS Note 161818.1) and the latest PSU or CPU. If you'd do that to your already emptied old home it will simply increase again your overall downtime.

And this is the reason why we recommend:
Always install into a new Oracle home beginning with Oracle Database 11.2 - don't erase your old home to reuse it unless there's no significant need for that procedure.

Thursday Nov 10, 2011

Upgrade & Migration Workshop in Singapore

Singapore 2

Thanks to everybody being there today in Singapore for our new
Upgrade and Migration to Oracle Database 11.2
workshop.It's actually great to be back :-)

In order to get the new slides for this workshop you might download them from here.

Thanks for your time and have successful upgrades and migrations!

Singapore Casino

Wednesday Oct 19, 2011

It's always the Optimizer, isn't it?! - Part 1

Wouldn't you agree?

My colleagues from the Optimizer Development might forgive me but a lot of people would say: "Everything went fine after upgrade - except for those tiny 3 queries!". And I know, you have tested a lot. I'd like to tell you about a few issues we've seen post upgrade with 11.2.0.2.

  1. You have captured your plans in Oracle 10.2 pre-upgrade.
  2. You have moved these plans from your SQL Tuning Set into the SQL Plan Baseline in Oracle 11.2.
  3. But the optimizer doesn't pick them although you have:
    (a) ACCEPTED and
    (b) FIXED them.

Why?

It might be worth a try to set this underscore parameter and test again:

_optimizer_use_feedback=FALSE

What does _optimizer_use_feedback mean?
You'd find some detailed information in our Upgrade Companion (MOS Note:785351.1):

Cardinality Feedback (Oracle Database 10g to 11g Change)
Cardinality feedback is an enhancement made to the Optimizer in Oracle Database 11g Release
2. Cardinality feedback compares cardinality estimates used to derive the plan with the actual
cardinality seen in the first execute. If the estimate is 2X off, the cursor is marked for hard parse
next time around. The cardinality information seen at first execute is supplied at the next hard
parse thus allowing the Optimizer an opportunity to improve on the plan now that it knows more
about the actual cardinality seen in the query. If cardinality feedback is used, it is displayed in the
section of the execution plan. Cardinality feedback works for predicates on tables, indexes and
group by clauses. It does not help for cardinality mis-estimates for joins. Feedback is not
persistent on disk, it resides in memory only. The Optimizer will need to "relearn" something if the
database is shutdown and restarted. (Related to _optimizer_use_feedback parameter.)

Besides that there were known issue in 11.2.0.1 (Bug 8608703 - SubOptimal Execution Plan created by Cardinality Feedback (Doc ID 8608703.8) - Bug 9342979 - Suboptimal plan change with cardinatilty feedback (Doc ID 9342979.8)) - but they seem to be fixed with patch set 11.2.0.2 and above.

While doing some research in our support portal (MOS) I accidentally found these interesting notes:

To be continued ...

Please don't take this as a general recommendation to set this underscore and switch off the functionality as this isn't a general recommendation!!! Be always careful with underscore/hidden parameters and always check back with Oracle Support - in most cases underscores slow down the upgrade and using underscores from previous releases has often a bad impact on performance!

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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