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VMWare Experts Program, Sydney

A few weeks back, I received an invitation from Don Sullivan to attend the Sydney version of the VMWare Experts Program. I worked with Don during our time at Oracle, and caught up with him again a couple of years ago at one of the Collaborate conferences. He had moved on to VMWare, and is still working for them today.

12c upuserxt.lst, upobjxt.lst & Oracle Maintained objects/users

Mike Dietrich has blogged recently about upuserxt.lst and upobjxt.lst and how to query them with external table. The first time I’ve seen those ‘.lst’ files, the default extension for sqlplus spool files, I wondered whether they were provided in ?/rdbms/admin on purpose, or if they were just some leftovers from some tests Oracle did before packaging the Oracle Home. Finally, I realized that they were there on purpose and that those ‘.lst’ are important files when upgrading to 12c.

Time for #GLOC, #SQLSatDallas, #DataSummit18

The next nine days, I’m traveling to three cities for four events. We’ll just call this the 9-3-4 gauntlet of speaker life. I booked this travel as four, one-way flights to get the itinerary
I needed to make the most of my schedule and will have breaks between each event to make sure I don’t kill myself my last two weeks at Delphix.

GLOC

ADWC – connect from your premises

In the previous post about the Autonomous Data Warehouse Service, I’ve run queries though the Machine Learning Notebooks. But you obviously want to connect to it from your premises, with SQL*Net.

CaptureADWCconnect001Of course the connection, going through the public internet, must be secured. If you already use a managed service like the Oracle Exadata Express Cloud Service, you already know how to do: download a .zip containing the connection string and the wallet and certificate for SQL*Net encryption.

Skip Scan 3

If you’ve come across any references to the “index skip scan” operation for execution plans you’ve probably got some idea that this can appear when the number of distinct values for the first column (or columns – since you can skip multiple columns) is small. If so, what do you make of this demonstration:

SQL Developer Web on the Oracle Cloud

You like SQL Developer because it is easy to install (just unzip a jar) and has a lot of features? Me too. It can be even easier if it is provided as a web application: no installation, and no java to take all my laptop RAM…
When I say no installation, you will see that you have some little things to setup here in DBaaS. That will probably be done for you in the managed services (PDBaaS) such as ‘Express’ and ‘Autonomous’ ones.

CaptureSDW010

Some ideas about Oracle Database on Docker

This is not a ‘best practice’ but just some ideas about building Docker images to provide an Oracle Database. I started with the images provided by Oracle: https://github.com/oracle/docker-images/tree/master/OracleDatabase/SingleInstance and this is great to validate the docker environment. Then I customized for my needs and here are the different points about this customization.

Do not send a huge context at each build attempt

I work by iteration. Sending a 3GB context each time I try a build is a no-go for me. Then I quickly stopped to put the Oracle installation .zip in the context of my build. I already blogged about this.

20 Indexes

If your system had to do a lot of distributed queries there’s a limit on indexes that might affect performance: when deriving an execution plan for a distributed query the optimizer will consider a maximum of twenty indexes on each remote table. if you have any tables with a ridiculous number of indexes (various 3rd party accounting and CRM systems spring to mind) and if you drop and recreate indexes on those tables in the wrong order then execution plans may change for the simple reason that the optimizer is considering a different subset of the available indexes.

FBIs don’t exist

This is a reprint (of a reprint) of a note I wrote more than 11 years ago on my old website. I’ve decided to republish it on the blog simply because one day I’ll probably decide to stop paying for the website given how old all the material is and this article makes an important point about the need (at least some of the time) for accuracy in the words you use to describe things.

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There’s no such thing as a function-based index.

Well, okay, that’s what the manuals call them but it would be so much better if they were called “indexes with virtual columns” – because that’s what they are and that’s a name that would eliminate confusion.

ADWC – the hidden gem: Zepplin Notebook

IMG_5339
In the previous blog posts I explained how to create, and stop/start the Autonomous Data Warehouse Cloud service. And I didn’t show yet how to connect to it. It is easy, from sqlplus or SQL Developer, or SQLcl.

But there’s something more exciting to run some SQL queries: the Oracle Machine Learning Notebooks based on Apache Zepplin. At first, I didn’t realize why the administration menu entry to create users in the ADWC service was named ‘Manage Oracle ML Users’, and didn’t realize that the ‘Autonomous Data Warehouse Cloud’ header was replaced by ‘Machine Learning’.