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March 2012

Sqoop /*+ parallel */

It’s often useful to keep one’s ear to the ground when one is responsible for database performance and/or efficiency — it’s a talent that I wish more DBAs had: a sense of curiosity about how the database is being used to support particular application use cases.

Today’s post deals with something rather basic, but it speaks to this idea of “agile” collaboration between developers and DBAs around something that has a lot of buzz right now: processing “Big Data” with Hadoop / MapReduce. In particular, a process that someone has already deemed to be “too big” to be accomplished within an existing Oracle database.

How much does IT cost?

One of my friends used to own a sandwich bar. He knew the exact profit margin on each product. He knew the impact of a price change from one supplier on each of the products he sold, as well as the overall affect on his profits.

So compare that situation with your average IT department, where to be frank, nobody has a bloody clue about costs. Yes, we all know the headline grabbers like licensing cost for Oracle and you can probably find the bit of paper that tells you the yearly hardware maintenance fee, but I’ve not encountered many companies that have a handle on the real cost of projects. If a company can’t say, “Project X cost £Y to complete and costs £Z a year to maintain and this is the breakdown of costs”, with a reasonable level of accuracy then they’ve failed.

Oracle Database Appliance – Urgent Patch 2.1.0.3.1

Just a quick heads up to the ODA customers — there is a critical patch 2.1.0.3.1 out that is applied on top of ODA patch bundle 2.1.0.3.0. This patch has an important fix for a bug causing ODA servers to shutdown in some situations when an ASM disk is lost. The patch number is 13817532 [...]

Oracle Database Appliance — Storage expansion with NFS (dNFS, HCC)

The biggest objection to Oracle Database Appliance (ODA) we hear from customers is about 4TB usable space limit (tripple mirrored 12TB of raw storage). I think most of the times this is more a perceived barrier rather than objective — more along the lines of being afraid to hit the limit if the system grows [...]

OUGN 2012 Third Day

The last day of the three (and second on the ferry and of the conference proper) had a lot of talks I wanted to see, especially Dan Morgan talking about “Insanely large Databases”. It was a good talk, with an interesting interlude when a very loud announcement let us know we had docked at Kiel. Dan handled it with aplomb. Dan was talking about one specific experience he had suffered recently and he covered quite a few things I did and some I planned to but never got that far – but he had more technical details about the issues he had encountered, so all in all probably of more immediate use to the audience than my talk. It was a very good session. I have to confess, there were times I laughed out loud as memories flooded in, prompted by his wise words – I fear others may have interpreted differently but, honestly, I was laughing tears of shared pain.

The fourth use-case for triggers

In our previous post we talked about three of the four use-cases we introduced. Triggers can:

  1. Assign/modify (row) column values.
  2. Execute insert/update/delete statements.
  3. Execute non-transactional stuff.
We've also discussed why indeed using triggers for above use-cases, should be considered harmful. Their automagic side-effects are often not expected by other programmers / users of the database application.

In this post we continue with use-case four. Triggers can:

  1. Execute select statements.

2001: Oracle Database Appliance by Dell — Déjà vu

Stumbled upon this Dell’s article from 2001 — The Oracle Database Appliance by Dell: Architecture and Features. The idea of appliance-like platform for Oracle database is obviously not new but the latest implementation of Oracle Database Appliance makes the most sense from all previous attempts (comments are open below to disagree if you’d like). What [...]

OUGN Spring meeting 2012

I had the great pleasure to spend the better part of last week at the Norwegian Oracle User Group’s spring conference. Martin Nash and I helped promote the Real Application Cluster platform on the attendees’ laptop in a program called RAC Attack.  RAC Attack has its home on the wikibooks website http://racattack.org where the whole program is documented and available for self-study. The purpose of the hands-on labs which Jeremy Schneider started a few years ago is to allow users to get practical experience installing Oracle Linux, Grid Infrastructure and the RDBMS binaries before creating a two node database. Following the database creation a practical session ensues which explains certain HA concepts with RAC such as session failover. We are planning on greatly enhancing the lab session as we go along. If you have any suggestions about what you would like to see covered by us then please let us know!

Coalesce Subquery Transformation - COALESCE_SQ

Oracle 11.2 introduced a set of new Query Transformations, among others the ability to coalesce subqueries which means that multiple correlated subqueries can be merged into a number of less subqueries.

Timur Akhmadeev already demonstrated the basic principles in a blog entry, but when I was recently involved into supporting a TPC-H benchmark for a particular storage vendor I saw a quite impressive application of this optimization that I would like to share here.

Another batch of Linux articles (RHCSA)…

I’ve just put another batch of Linux articles live.