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February 2015

Exadata & In-Memory Real World Performance Artikel (German)

Heute wurde auf "informatik-aktuell.de" ein aktueller Artikel von mir veröffentlicht. Es geht darin um die Analyse eines Falles bei einem meiner Kunden, der auf Exadata nicht die erwartete Performance erreicht hat.

In dem Artikel werden unterschiedliche Abfrage-Profile analysiert und erklärt, wie diese unterschiedlichen Profile die speziellen Features von Exadata und In-Memory beeinflussen.

Teil 1 des Artikels
Teil 2 des Artikels

Free In-Memory Column Store Workshop with Maria Colgan

I am very proud to be able to announce a free workshop on Friday the…

Public Appearances 2015

Here’s where I’ll hang out in the following months:

11-12 Feb 2015: IOUG Exadata SIG Virtual Conference (free online event)

  • Presentation: Exadata Performance: Latest Improvements and Less Known Features
  • It’s a free online event, so sign up here

18-19 Feb 2015: RMOUG Training Days (in Denver)

  • I won’t speak there this year, but plan to hang out on Wednesday evening and drink beer
  • More info here

1-5 March 2015: Hotsos Symposium 2015

Quick diff for two pieces of text in vim

Sometimes you need to see the difference between two pieces of console output. When I research, this can be two stacktraces, but also /proc//maps and smaps output; really anything. Of course, there’s diff, but the diff output is not very visual. Also, diff doesn’t do diffing between more than two files.

This can be done reasonably simple in vim. Here’s how to do that:
1. start vi; vi
2. do a vertical split using a new buffer; :vnew
3. open the first (left side) file; :r path/file or goto insert mode (esc i) and paste text.
4. goto the second window: ctrl+w ctrl+w
5. open the second (right side) file; :r path/file or goto insert mode (esc i) and paste text.
6. diff the two windows; :windo diffthis
7. turn diff mode off; :windo diffoff

How to Use an ASH Report and Why

Active Session History, (ASH) reports are one of my favorite when investigating a performance issue.  The biggest challenge I think that faces many administrators is to know when to turn to an ASH report and how to use the report to diagnose an issue.

Video Tutorial: XPLAN_ASH Active Session History - Part 3

The next part of the video tutorial explaining the XPLAN_ASH Active Session History functionality continuing the actual walk-through of the script output.

More parts to follow.

iTunes 12.1 skips after recent update

iTunes started skipping on my PC after a recent update (end of Jan 2015). It is version 12.1 of iTunes.

iTunes skips when using Chrome, mostly.

That’s enough search-friendly lines to help the web crawlers get here. Apologies to my normal visitors, this is obviously nothing to do with Oracle databases, development or my usual ramblings. Go read something else unless you landed here looking for help with skipping iTunes playback.

iTunes on my laptop wanted to update a few days ago so I let it. Next time I fired iTunes up, I was annoyed to discover that a track I had recently uploaded, from a compilation CD I have of 60’s classics, was poor quality and skipping. Except that the next few tracks also skipped a little, old favorites I knew were fine. I did a quick web search but most of the references were 4 or 5 years old. The skipping was getting worse so I shut down iTunes and used a…. CD player.

To N or Not to N, is SYS_OP_C2C the Question; Oracle NVARCHAR Slow?

February 8, 2015 I was recently contacted about an odd performance issue with a software product named TDM, where certain SQL statements submitted to an Oracle 9.2.x database required roughly 30 seconds to execute when a nearly instantaneous response was expected.  The person who reported the issue to me provided a sample SQL statement that […]

Functions & Subqueries

I think the “mini-series” is a really nice blogging concept – it can pull together a number of short articles to offer a much better learning experience for the reader than they could get from the random collection of sound-bites that so often typifies an internet search; so here’s my recommendation for this week’s mini-series: a set of articles by Sayan Malakshinov a couple of years ago comparing the behaviour of Deterministic Functions and Scalar Subquery Caching.

http://orasql.org/2013/02/10/deterministic-function-vs-scalar-subquery-caching-part-1/

http://orasql.org/2013/02/11/deterministic-function-vs-scalar-subquery-caching-part-2/

The Hitchhiker’s Guide to the EXPLAIN PLAN Part 35: Robust v/s optimal query execution plans

A subset of all possible execution plans can be described as robust. While such solutions are not always quite optimum, they are almost always close to optimum in real-world queries, and they have desirable characteristics, such as predictability and low likelihood of errors during execution.(read more)