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June 2017

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Unpivot

An interesting observation appeared recently as a side-channel on a question on the OTN database forum – how does Oracle execute an unpivot() operation. Here’s an example of such a query:

E4 Session Developing Agnostic Data Services

Thank you for all attending my virtual session Developing Location and Technology Agnostic Data Services at Accenture Enkitec's E4 2017 Conference.

Here is the presentation deck for your reference. http://www.proligence.com/pres/e4_2017/e4_17_data.pdf

As always, I will appreciate your feedback--the good, the bad and the ugly.

NYOUG Session How Oracle Buffer Cache Works

Thank you all for coming to my session How Oracle Buffer Cache Works at New York Oracle User Group Summer General Meeting in New York City.

You can download the session and scripts used for the demo here.

Presentation : http://www.proligence.com/pres/nyoug17/nyoug17_buffercache.pdf
Scripts : http://www.proligence.com/pres/nyoug17/nyoug17_buffercache_scripts.zip

As I mentioned during my talk, you may find these blogposts helpful to understand this more:

How Oracle Locking Works http://arup.blogspot.com/2011/01/how-oracle-locking-works.html

Where in the World is DBA Goth Girl- Week 24

I just returned from a week in Paris and it was fantastic!

12cR2 PDB refresh as a poor-man standby?

Disclaimer

My goal here is only to show that the Refreshable PDB feature works by shipping and applying redo, and then can synchronize a copy of the datafiles. I do not recommend to use it for disaster recovery in any production environment yet. Even if I’m using only supported features, those features were not designed for this usage, and are quite new and not stable yet. Disaster Recovery must use safe and proven technologies and this is why I’ll stick with Dbvisit standby for disaster recovery in Standard Edition.

This post explains what I had in my mind whith the following tweet:
CapturePoorManSBY

dbms_sqldiag

If you’re familiar with SQL Profiles and SQL Baselines you may also know about SQL Patches – a feature that allows you to construct hints that you can attach to SQL statements at run-time without changing the code. Oracle 12c Release 2 introduces a couple of important changes to this feature:

  • It’s now official – the feature had been copied from package dbms_sqldiag_internal to package dbms_sqldiag.
  • The limitation of 500 characters has been removed from the hint text – it’s now a CLOB column.

H/T to Nigel Bayliss for including this detail in his presentation to the UKOUG last week, and pointing out that it’s also available for Standard Edition.

Getting started with VPD in #Oracle

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Predicate relations or join on clause

Some of my friends vehemently prefer the SQL-89 predicate relations definition of joins.

Some of my friend vehemently perfer the SQL-92 “join on” clause, aka ANSI joins (which always puzzles me since I think both are defined in ANSI standards.)

 

Some folks (and this probably doesn’t include my friends) have called the Oracle join specification (+) “an abomination.”

I think each has strong points and drawbacks. In Oracle both are still legal.

In which syntax is it quicker to discover all the tables involved in a particular query? (hint: the one where you list all the tables immediately after the from clause.) Of course inline views and “with” common table expressions have diluted that old advantage of ’89.