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November 2014

Plan puzzle

I was in Munich a few weeks ago running a course on Designing Optimal SQL and Troubleshooting and Tuning, but just before I flew in to Munich one of the attendees emailed me with an example of a statement that behaved a little strangely and asked me if we could look at it during the course.  It displays an odd little feature, and I thought it might be interesting to write up what I did to find out what was going on. We’ll start with the problem query and execution plan:

Will the real data virtualization please stand up?

There is a post from a good friend at Oracle entitled “Will the REAL SnapClone functionality please stand up?” and, as well-written and technically rich as the post is, I am particularly moved to comment on the very last and conclusive sentence in the post…

So with all of that, why would you look at a point solution that only covers one part of managing your Oracle infrastructure?

Removing Redundant Startup/Restart for the OMS Service in Windows

I’ve been told many times that the OMS for EM12c can take quite some time to start on Windows.  Some told me it took anywhere from three to up to fifteen minutes and wanted to know why.  I’ve done some research on the challenge and it is a complex one.

Shrink Tablespace

If you start moving objects around to try and reclaim space in a tablespace there are all sorts of little traps that make it harder than you might hope to get the maximum benefit with the minimum effort.  I’ve written a couple of notes in the past about how to proceed and, more recently, one of the difficulties involved. This is just a brief note about a couple of ideas to make life a little easier.

HOWTO: Validate XML content against an XML Schema

Somewhere on this site is a post regarding how to validate against an XML schema…

Will the REAL Snap Clone functionality please stand up?

Every so often our competitors like to spread false information about our solutions so as to gain unfair advantage. I wanted to address this for the Enterprise Manager Snap Clone functionality, so this blog post describes the Snap Clone solution as it currently stands (November 2014).

Let’s start by introducing Snap Clone functionality. I blogged on that a few months back, but a few months can be an eternity in software development terms, so here’s an update on the salient points of what Snap Clone does for you over the various EM releases:

Foreign Archived Log in #Oracle – what does it mean?

When you look into V$RECOVERY_AREA_USAGE, you see a strange row at the bottom:

Parallel Fun

As I write, there’s an ongoing thread on Oracle-L that started with the (paraphrased) question: “I’ve got this query that returns 7 million rows; when I change it to ‘select count(*)’ it returns in 4 seconds but when we display the full result set on screen it takes hours, and every second or two the screen pauses; how do I make it go faster.”

The general rapid response was: “You shouldn’t be running 7M rows to a screen – the time is the time for the network traffic and display.”

Quick Links to Helpful Literature on Oracle Database In-Memory Column Store.

I’m surprised to find that Google is not cleanly ranking the helpful set of blog posts by Oracle’s Maria Colgan on the Oracle Database 12c In-Memory Column Store feature so I thought I’d put together this convenient set of links. Google search seems to only return a few of them in random order.

Over time I may add other helpful links regarding Oracle’s new, exciting caching technology.

Starter Information

Getting Started With Oracle Database In-Memory. Part I.

Getting Started With Oracle Database In-Memory. Part II.

Getting Started With Oracle Database In-Memory. Part III.

Audio semi-Visual Presentation on Clustering Data in Oracle

I suppose it had to happen eventually but one of my presentations has ended up on YouTube. It’s a recent presentation I did for the Oracle Midlands user group in September.

The topic is (as the title of this blog post hints at!)Boosting select performance by clustering data. The video consists of the slides I presented, changing as the presentation progresses, with my audio over the top. It goes on for a bit, close to an hour, but you could watch a section and then go and do something else before watching a bit more.

I have to say, it is very odd hearing my voice (and the slight touch of the “brummie” {Birmingham} accent coming through) and I do wince at the places where I blather or say something slightly wrong or make a joke that involved a visual element that is lost. Oh well, at least you don’t see me wandering around and jumping up,literally, to point out bits on the slides.