With apologies to Dr. Seuss.
Did I ever tell you the makers of RAC
had seven features and named each flashback?
Well they did, and it wasn’t a smart thing to do.
You see, when the customers wanted a clue
as to how to keep data from getting deleted
the RAC folks said “flashback” and customers heeded.
They turned on all seven of those flashback features
Each one was a slightly dissimilar creature.
Some used the UNDO, some used flashback files
Some just renamed tables to bin$ styles.
One was a place you keep things for recovering
Another was just for forensic discovering
With so many features called by the same name
when thinks broke no one knew just which one they should blame.
Before I joined Blue Gecko, I did independent remote DBA work, and called myself ORA-600 Consulting. Stemming from my hair-raising experiences in the trenches at Amazon in the late ’90s / early 2000s, I decided to specialize in emergency DBA work for companies in the midst of crises (I know, great idea for someone who wanted to get away from the Amazon craziness, right?).
One day in 2009, a company in Florida called my cell phone at 2AM. They described their problem as follows:
In my previous post, I made the comment:
In general, if you have a three-column index that starts with the same columns in the same order as the two-column index then the three-column index will be bigger and have a higher clustering_factor.
So what scenarios can you come up with that fall outside the general case ?
Alternatively, what argument could you put forward that justifies the general claim ?
I’ll try to respond to comments on this post a little more quickly than the last one, but I still have quite a lot of other comments to catch up on.
If you are not familiar with R, this is the description from the R site: R is a language and environment for statistical computing and graphics. I encountered R at the Erasmus university, where I am working on a project with DNA data which is put in an Oracle database (see: http://huvariome.erasmusmc.nl/ (It’s down at the moment)).
I mentioned this when I blogged about my 11gR2 Virtual RAC install on Windows 2008. It came up in a conversation with Niall Litchfield at UKOUG 2011 and I’m reminded of it again today, after doing an 11gR2 install on Windows XP to double-check my answer to a question. Oracle database installs on Windows are so incredibly easy!
Now I’m not saying I would want to run Oracle on Windows out of choice. I’m a Linux fanboy, as you probably know, but even the most staunch Linux fan would have to agree that Oracle installs on Linux require quite a few prerequisite steps, even with the oracle-validated package. There is just nothing to do on Windows except put in the CD (iso image) and go…
Just a quick heads-up for anyone who is interested in getting hold of a free copy of
OCA Oracle Database 11g: SQL Fundamenta
There are two free e-books to be won. The two people that contact Sunil Chakravarthy (email@example.com) giving the best reason why they want a free copy of this book win.
Please don’t contact me about this offer. It’s not my book and it’s not my competition. Good luck.
Browsing a little history recently I came across a note I’d written about the new-style index hint. In that note I claimed that:
… the index has to start with the columns (product_group, id) in that order – with preference given to an exact match, otherwise using the lowest cost index that starts the right way.
On reading this statement I suddenly realised that I hadn’t actually proved (to myself, even) that if I had the indexes (product_group, id) and (product_group, id, other_col) then a two-column hint forced Oracle to use the two column index in all (legal) circumstances.
So, tonight’s quiz – are there any edge cases, and what easy ways can you think of to prove (or disprove) the claim for the general case.
The framing clause brings the "window" to window functions. Through it you define a window, or frame of reference if you prefer, that slides along a result set generating values such as running totals and moving averages. The framing clause is ideal when you can arrange a business question such that an answer comes from applying an aggregate function to a range of rows that slides or stretches smoothly as focus moves from one row to the next.
Several years ago I met Arjen Visser and Bertie Plaatsman from Dbvisit and they told me about their standby database product, which is a replacement for Data Guard. Now I don’t spend much time on non-Oracle products, but this one was interesting to me as it works on Standard Edition, unlike Data Guard which is an Enterprise Edition option. From that point onward I kept seeing Arjen and conferences and telling myself I really should take a look at the product.
Over last year I bumped into Arjen at a few conferences, along with some other members of the company (Eric, Mike and Vit). They are a cool group of people, so my interest in their products was ignited again. Finally, after several years of showing interest I tried out the standby product towards the end of last year, which resulted in the following article.
Chris Date is one of the founding fathers of relational databases. Having worked with Ted Codd at IBM during the time when relational databases were being defined gives Chris a perspective that most of us just don’t have. I’ve had the good fortune to hear him speak in the past (at the Hotsos Symposium) and thought I would do a quick post to highlight the fact that he is scheduled to speak in Dallas the week of Jan 30. Method-R is hosting the event in the Enkitec training facilities in Dallas. So maybe I’ll get to hang around with Chris and Cary that week – that would be cool! Anyway, there are actually 2 classes: