September 2009

SMART goals

I was just reviewing the written goals for a project I've started working on and after looking at a few of them, I was reminded of how important it is to make sure your goals are "SMART".

For example, one of the project goals is: To create a standard framework that supports high levels of service. Hmmm... When I read that goal, I found myself thinking of the concept of SMART goals that I learned a long time ago. Somehow this goal doesn't seem to fit the SMART paradigm.

So, what is a SMART goal?

Latency Hiding For Fun and Profit

Yep, another post with the word ‘latency’ written all over it.

I’ve talked a lot about latency, and how it is more often than not completely immutable. So, if the latency cannot be improved upon because of some pesky law of physics, what can be done to reduce that wasted time? Just three things, actually:

  1. Don’t do it.
  2. Do it less often.
  3. Be productive with the otherwise wasted time.

The first option is constantly overlooked – do you really need to be doing this task that makes you wait around? The second option is the classic ‘do things in bigger lumps between the latency’ – making less roundtrips being the classic example. This post is about the third option, which is technically referred to as latency hiding.

Everybody knows what latency hiding is, but most don’t realise it. Here’s a classic example:

I need some salad to go with the chicken I am about to roast. Do I:

(a) go to the supermarket immediately and buy the salad, then worry about cooking the chicken?

OR

(b) get the chicken in the oven right away, then go to the supermarket?

Unless the time required to buy the salad is much longer than the chicken’s cook-time, the answer is always going to be (b), right? That’s latency hiding, also known as Asynchronous Processing. Let’s look at the numbers:

Variable definitions:

Supermarket Trip=1800s

Chicken Cook-Time=4800s

Calculations:

Option (a)=1800s+4800s=6600s (oh man, nearly two hours until dinner!)

Option (b)=4800s (with 1800s supermarket time hidden within it)

Here’s another example: You have a big code compile to do, and an empty stomach to fill. In which order do you execute those tasks? Hit ‘make’, then grab a sandwich, right?

4th Planboard DBA Symposium: Registration now open

On November 17 Planboard will run her 4th Dutch DBA Symposium and the registration is now open. This “for Dutch DBA’s, by Dutch DBA’s” symposium has become the place to be for the serious DBA who wants to share his or her knowledge with other DBA’s in an open environment with plenty of networking time [...]

nonsense correlation

I was doing a little light reading on my Saturday night in my Oxford Dictionary of Statistics by Graham Upton and Ian Cook and came across this definition:nonsense correlation: A term used to describe a situation where two variables (X and Y, say) are correlated without being causally related to one another. The usual explanation is that they are both related to a third variable, Z. Often the

Spotting the Red Flags (Part 1 of n)

As a consultant I get to see many different systems, managed by different people. A large proportion of these systems are broken in exactly the same ways to others, which makes spotting the problems pretty straightforward! It occurred to me at some point that this is a bit like a crime scene – somebody had murdered the system, and it was my job to find out ‘whodunnit’, or at least ‘whatdunnit’. The ‘what’ is quite frequently one (or few) actions performed by the administrator, normally with good intention, that result in system performance or availability carnage. I call these actions ‘Red Flags’, and spotting them can save a lot of time.

A couple of years ago at the Hotsos conference, I did a small impromptu survey. It’s not all that often that you have 500 Oracle geeks in a room that you can solicit opinion from, so it seemed like a good chance to cast the net for Red Flags. I seeded the process with a few of my personal favourites and then started writing as the suggestions came in. Here are the ‘seed’ entries:

  • Any non-default setting for optimizer_index_cost_adj
  • Carefully configured KEEP and RECYCLE pools
  • Multiple block sizes
  • Some kind of spin_count configuration

Remember, these are not necessarily the wrong thing to do to your system, but they probably are. That’s why they attract my attention in the first instance.

I got a whole load of responses. Of those responses, some had missed the point and just identified something that was broken. This is more subtle than that – these are things that are forensic evidence of system homicide. Some of the decent ones I got back follow:

The best flowchart ever

This was forwarded to me and I totally laughed out loud. I've seen a lot of flow charts (mostly of the boring technical sort), but this is my absolute all-time favorite! Zoom in on it or visit the originating site to see it better.

It's a flow chart of the song "Total Eclipse of the Heart".

Happy Birthday, OFA Standard

Yesterday I finally posted to the Method R website some of the papers I wrote while I was at Oracle Corporation (1989–1999). You can now find these papers where I am.

When I was uploading my OFA Standard paper, I noticed that today—24 September 2009—is the fourteenth birthday of its publication date. So, even though the original OFA paper was around for a few years before 1995, please join me in celebrating the birthday of the final version of the official OFA Standard document.

Resumes, interviews and truth in advertising

OK...what's the deal with resumes that say one thing (so that a candidate looks nearly perfect) and then you interview them and find out they can barely spell Oracle? I'd think that if your resume says you've been working with Oracle since 1988 and have worked extensively with PL/SQL, you'd know what a REF CURSOR is or maybe even know a bit about collections or something, right? I asked one candidate these questions and they said they'd never ran into those 'features'. So finally, just for fun, I asked "On a scale of 1-10, with 10 being expert, where would you rank yourself in terms of your PL/SQL proficiency?" The answer: "Well, I suppose it's a bit conceited to give yourself a 10, so I'll just be humble and say 9."

Are you kidding me? Really?

Dynamically Switching PeopleSoft Temporary Records between Global Temporary and Normal Tables during Application Engine Programs

I am working on a Time & Labour system. We run the main T&L process in different modes. There is a company wide overnight batch process, but individual parts of the company can run the process for their section during the day to process exceptions and to generate schedules. This is done with a custom AE program that calls the delivered TL_TIMEADMIN.

Running on Oracle 10gR2, we have faced performance problems caused by contention between concurrent truncate operations in these processes (see Factors Affecting Performance of Concurrent Truncate of Working Storage Tables).

Dynamically Switching PeopleSoft Temporary Records between Global Temporary and Normal Tables during Application Engine Programs

I am working on a Time & Labour system. We run the main T&L process in different modes. There is a company wide overnight batch process, but individual parts of the company can run the process for their section during the day to process exceptions and to generate schedules. This is done with a custom AE program that calls the delivered TL_TIMEADMIN.

Running on Oracle 10gR2, we have faced performance problems caused by contention between concurrent truncate operations in these processes (see Factors Affecting Performance of Concurrent Truncate of Working Storage Tables).