Always Learning

Jonathan Lewis Seminar in Dallas

I got to hear Oracle performance guru Jonathan Lewis today in an all-day seminar in Dallas. "Writing Optimal SQL" was part 2 of a two-part series here in Dallas, sponsored by Dallas Oracle Users Group (DOUG).

Jonathan started out by reviewing some general principles, such as the importance of design and optimizing for the global situation (many queries) not just a single query. "Making me go fast might make you go slower," he said.

Performance comes from precision in selecting just the blocks and rows you need to select, and from the structure of the data (where it's located).

My favorite part of the seminar was his discussion on coding style for SQL, a topic that is often ignored in performance discussions. His view that "Computers are cheap; humans are expensive" is one that I've been preaching for years in my SQL and PL/SQL classes.  "You have two audiences," I tell my classes, "the compiler, and the poor person who comes after you to maintain your code.  Be kind.  Someday that person will be you." Jonathan's take is that you should write SQL as a close translation of the business purpose of the query, and only fiddle with it if performance isn't acceptable.

He also suggested: "Don't tune the SQL; tune the end users," meaning that if a requirement is unclear or the data creates unexpected results, go back to the person requesting the report and get clarification instead of burning a lot of time over-engineering the solution to fit every possible case.

This talk could easily have been titled, "Unintended Side-Effects of SQL" because Jonathan went through many scenarios in which results differed from what might have been expected, and why it turned out that way.

It was a great session.  Thanks to Speak-Tech  and to DOUG's Mary Elizabeth McNeely, president and programs chair, for bringing Jonathan Lewis to town.

Oracle 11gR2 Podcast by Tom Kyte

Tom Kyte recorded a podcast this month about the new features of Oracle Database 11gR2. The podcast, part of the Oracle Database podcasts series, can be accessed here:

http://www.oracle.com/database/podcasts.html

In it, he describes an exciting new feature: the ability to compile stored procedures, packages, etc. while users are online using the same schema! The feature, called Edition-based Redefinition, refers to the current objects as an "edition".  The developer creates a child edition based upon the current one, then does development against the child edition. When it comes time to switch over, new sessions can begin using the new edition, as existing sessions continue to use the old. An upgrade that used to take an hour of downtime for compilations can appear to users to take no time at all. It still takes an hour to compile, he said, but the users are not locked out of the system while it's happening.

He also talks about the ability to create a table, but defer to allocation of storage until the table is first used. This will make it much faster to install complex software applications that have many optional tables in them. Only the metadata in the data dictionary will be created during the install, and tables never used will therfore not take up space.

It's a short talk, about 10 minutes, but well worth listening to.

Business travel tip: Dallas-Fort Worth (DFW)

It took me a while to get used to the cloverleaf sprawl that is Dallas-Fort Worth International Airport (airport code DFW). But now that I've been using it regularly, I find I like its layout a lot.   Besides, the twisty-turny access roads remind me of the old Autopia attraction in Disneyland's Tomorrowland.

Here are some random tips to know about DFW.

It's big.  There are five terminals, A through E.  If you look at a map of the place, you'll see that some of the parking lots are shaped suspiciously like terminals. It looks like they could add three entire new terminals in the future.

A freeway runs through it:  The airport terminals are divided by a north/south freeway, which is also a toll road. You take a ticket when entering, and pay upon leaving. Your car's license plate number is printed on the ticket (it's entered by the tollboth attendant when you enter.) If you just drive straight through, the toll is $2; if you linger a while (like when you drop off or pick up someone), it actually costs less.

To the left, to the left:  All exits to the terminals from the tollway are left exits, no matter which side of the tollway the terminal is on. Cloverleafs spin you around to the terminals on the opposite side.

Parking, lots: There are four types of parking, if you're driving in from the Dallas-Fort Worth area (the "Metroplex"). In order of cost (low to high), they are:

• Remote North and Remote South: These are just outside the tollway, at each entrance. Cheapest parking, large buses take you to the terminals.

• Express North and Express South. These are just INside the tollway, cost a little bit more, but have some nice amenities. Mini shuttles instead of large buses pick you up at your car, and drop you back at your car upon return. There's a free bottle of water when you check in, and the shuttles are dedicated to specific terminals so the trip is shorter.  Express North is the smaller of the two, but nicer; it fills up fast.

• Terminals A-E Infield.  This is an open air parking lot at each of the terminals. Quite a walk from the terminal. The other down side is that sometimes you may leave from one terminal, but your return flight lands at another. So it's a bus ride to get back to your car.

• Terminals A-E Parking Garages. The priciest option, but closest to the terminal.

Central air:  All the rental cars are in a central facility. From the terminal curbs, take the Rental Car Center bus.

Hang up and park: There is no cell phone lot at DFW as at many airports. If you're waiting for someone, use one of the Remote lots: the cost is only $0.50 for the first hour.

Refresh Everything, as long as it's Pepsi:  DFW is a Pepsi place. All the shops and vending machines sell Pepsi products, along with juices and water. If you're a Coke or Diet Coke person, though, don't despair.  The McDonald's outlets in the various terminals sell Coke products.

Take the A(irport) train: A computer controlled elevated train system called SkyTrain goes to all the terminals, and it's inside the secure area so you don't need to go through security again to use it. There are two stops per terminal.  Take the escalator upstairs, board the train, then take the escalator downstairs to reach your gate. If you're outside the secure area, you have to leave the terminal and use buses that load out front at the curb. It's called Terminal Link.

Controlling Controlfile Backups

Did you know that you can control the name of your controfile trace backups? I didn't, until Bob Morgan of Stonehill College in Easton, MA pointed out some additional syntax in the ALTER DATABASE command.

I already knew that you could control the filename and location when backing up the controlfile in binary, via:

ALTER DATABASE BACKUP CONTROLFILE TO '<pathame>';

And I knew that you could get a text copy of the commands necessary to rebuild the controlfiles, via:

ALTER DATABASE BACKUP CONTROLFILE TO TRACE;

The resulting text commands are placed in the user's trace file for the session. To find the proper trace file requires knowing the session number; it's in the filename.  (Though I usually cheat, and go to the directory pointed to by the user_dump_dest parameter, sort by modification time, and my session is near the top.)

What Bob pointed out was the variation:

ALTER DATABASE BACKUP CONTROLFILE TO TRACE AS '<filename>';

This still writes to the backup_dump_dest directory, but names the tracefile with your choice of filename instead of the default one that includes the session number.  Much easier to find.

Thanks, Bob!

Training Tip: When You Train, Train

I think it was The Inner Game of Tennis, by Timothy Gallwey, that first taught me this lesson: when you are preparing for a class, prepare. But when it comes time to stand up in front and start the class, train.

You may not feel as prepared as you would like to be. The conditions may not be as ideal as you would like them to be. But once class starts, you are who you are, and the conditions are what they are. You go for it.  You give your current self to the group, just as you are, and you do your best. You train.

It's hard to stop the inner, critical voice that reacts when you make a mistake. It's hard not to wince or get flustered when your lesson plan just plain doesn't work for a given group. But training is as much a performance as a play (except that many of the lines are not scripted), and the show must go on. Adapt, go where it takes you in the moment.

Of course, you can and should review your performance in the classroom. Every time. But you do that afterwards, when the room is empty or you're at yet another chain restaurant having dinner. There have been weeks when I've devoted my hotel time to staying one day ahead of the students, constantly reviewing the day just past and prepping like mad for the day to come.

Disney is a model for me in this regard. In their theme parks, they have "on stage" and "off stage" areas. When you're on stage, in front of paying customers, you're expected to be in character the whole time, even if you're not on duty and just passing from one place to the next. No gossiping about your friends or school, no talk of religion, politics, or sex. That's for off stage, when you're behind the scenes. Some criticize this, saying that it is artificial and inhumane for workers to be unable to be themselves. But I think it's the one key thing that makes going to a Disney park different than other ones. You're immersed in the story, and they're careful to eliminate anything that distracts from that experience.

When you're training, you're on stage too. Play the part the best you know how. Then later, off stage, plan how you're going to make it an even better show next time.

Training Tip: Training By Walking Around

In his best-selling business book In Search of Excellence, Tom Peters profiles companies such as Hewlett-Packard and United Airlines that practice "Management By Walking Around" (MBWA for short). Management is encouraged to get out of the office and into the field as often as possible to see things firsthand.

Too often, trainers feel constrained by the podium or other setup at the front of the room. They lecture from one spot, and answer questions from the front as well. "Training By Walking Around" means circulating in the room, teaching from various points.

Using a variety of media (computer, white board, easel, etc.) can help get you moving. It also provides variety to hold the attendees' attention.

This is especially important during lab exercises. It's tempting to retreat behind the front desk at such times; after all, you've been standing and talking, and now is your chance to sit, right? Wrong. Try this experiment: during a lab, ask if anyone needs anything.  Usually, you'll get no responses.  A minute later, casually get up and walk up and down the aisles. Chances are, someone will stop you and ask a question.

I will usually sit for the first five to ten minutes of a lab, then circulate, asking if everyone has gotten started okay. After another five to ten minutes, I'll circulate again, asking if anyone needs "another pair of eyes" to look at an error message.  Before the end of the lab, I'll make another pass silently. Usually by then people are stuck on a particular problem and will call me over as I pass by them.

I've even taught from the back of the classroom. I'd been presenting for a while, and could tell the group needed an energizer.  So I had them all stand and turn around, and I walked to the back (which was now in front of them.)  I did a contest quiz with a prize -- but because they were facing away from their notes and the computers, they couldn't reference them! We laughed about this, the act of standing re-energized the group, and we continued normally afterwards.

Training Tip: When to Ignore Advice

One of my earliest mentors in training gave me many immensely valuable pieces of advice.  And two that I've learned to ignore. I was thinking about this today while re-reading an old classic, Teacher as Servant: A Parable, by Robert K. Greenleaf (now out of print, but available used). So, here are two bits of advice I learned to ignore.

1. "Always perpetuate the illusion that in the classroom, you are God."

By that, I'm sure he meant to say that one must establish and maintain credibility. Once credibility is lost in a class, you seldom have the chance to regain it with that group. It's also important to maintain the authority that keeps you in control of the classroom process. But I've found it more useful to consider myself a servant of the group than its master. Yes, it's my job to maintain control; but only because they're paying me to do it, and because it serves their best interests for me to do so.

As usual, there are exceptions to every rule. I had one class that consisted entirely of highly-paid business consultants. I was told up front by their manager that it was a smart-alecky group that would give me trouble unless tightly managed. So I went in with the Top Gun approach, very authoritarian, but at the same time letting them know that "You're the best - but we're going to make you better."

2. "When you are doing class introductions, try to identify up front who the troublemakers are."

I tried this exactly once.  And I got what I expected: troublemakers. I haven't done it since. Now I expect up front that everyone in class is going to have fun, learn a lot, and contribute. It doesn't always happen that way, of course, but I think my expectations and mindset help it to happen more than it otherwise would.

The night before a class, as I'm falling asleep, I repeat to myself the affirmation (in present tense), "This is the best class I've ever had."

Tom Kyte's New Years Resolutions

Anyone who knows me knows I'm a BIG Tom Kyte fan.

Tom's published his list of New Years Resolutions for 2009, and the top of the list is "Practice a restore at least once a month."  You can read the rest of the resolutions here:

http://www.oracle.com/newsletters/information-indepth/database-insider/jan-09/kyte.html

(Thanks to Chen Shapira on Twitter for the pointer to this.)

Training tip: Teleconference Don'ts

Esther Schindler of CIO.com has a great article on PC World, listing 17 Telecommuting Disadvantages. One of them, #8,  is all about the annoyances of teleconferences -- but if you flip those annoyances around, they become training tips.

...people who lead teleconferences (with a half dozen participants) and start out by saying, "Who's here?" Doing so makes everyone on the phone wonder if it's their turn to speak up...  

Tip: take roll call instead, using the list of invited participants. Starting out this way also puts you squarely in control of the meeting. If possible, use web conferencing where rollcall is always available on the screen.

Organizers who show up late. Telecommuters are stuck listening to music-on-hold for ten minutes, during which they wonder, "Was today the right day? Did I miss the meeting?"  

Tip: Be there early if you're leading a session. Just like in the classroom, being early means you get to welcome everyone individually and establish rapport before the group session starts.

People who refer to a lot of visuals without bothering to send the file to telecommuters; and then they don't refer aloud to the data they're pointing at. 

Tip: Reference at least the slide title (and slide number -- you do put slide numbers on your slides, don't you?) when referring to visuals.

[A big thank you to Twitter user Reg Saddler (zaibatsu) for the link to this great article!]

Training Tip: Nearly Free Laser Pointer

When I got started in training, the pencil-type laser pointer was over $100. Needless to say, I found other ways to point at the screen  (hand shadows being the primary one).

Recently, I finally broke down and got a laser pointer, which I keep in my trainer kit. The cost?  Only $3, in a clearance bin at Walgreens. It was sold as a cat toy: a way to put a spot of light on the wall for cats to chase around. (It also puts up an image of a mouse, a butterfly, a star, and my favorite, a smiley face.)

The use of laser diodes in mass-market equipment such as CD and DVD players has lowered their production cost so far that now they can be sold as toys, not $100 professional tools.  I don't care what it says on the package, it's a dandy training aid.

On the other hand, training is often compared to herding cats, so maybe the package description is appropriate.

NOTE: Do not put this in your carry-on luggage. It's considered a weapon and forbidden by the TSA, so pack it with your trainer kit in your checked luggage.