This post is part 30 of a 30-part series about the Who is Active stored procedure. A new post will run each day during the month of April, 2011. After April all of these posts will be edited and combined into a single document to become the basis of the Who is Active documentation.
Pop quiz: What happens when you promise to write 30 posts on a topic, but you don’t plan properly and lose a bit of steam toward the end?
Answer: A recap post, a day or two early! Woo hoo!
The month started with a few introductory posts. A history of monitoring (from my point of view), some information on Who is Active’s design philosophy, and a few words on the Who is Active license.
The key takeaways from these first posts? The monitoring story has been pretty poor for most of SQL Server’s history. It’s better now, but it’s still a lot of work. Who is Active was created to make things more accessible. It’s free, with a few restrictions designed to keep people who make money from monitoring from making money on Who is Active. Anyone else can and should use and enjoy.
Next I got new users up to speed. My post on installation covered security considerations, followed by a post on why you may not see as much data as you're used to when you first start using Who is Active. I continued with a post on the various options supported by the procedure (plus a nod to the online help mode) and another post describing the default output columns.
One of the more important posts of the month described how Who is Active treats active requests and sleeping sessions. This can be a confusing area for new users, since it's not always obvious what's going on unless you're looking in the right place at the output (the [status] column).
Once the refresher was finished I began covering some of the basic options exposed by the procedure. Filters were one of the first things I implemented, so it was a logical place to start (the "not" filters came much later). Seeing the query text is a key part of the procedure's functionality, and that was next on my list. If you're not sure what the [sql_text] column means, this post will set the record straight.
The ability to see the query text is nice, but so is the ability to get a query plan--and of course Who is Active supports that too. And since everything a query does is transactional, the procedure allows users to collect information about what those transactions are up to.
The next section of the month was all about query processing. I started with a couple of background posts: One on how the query processor works (at a somewhat high level), and another on what blocking really means.
Who is Active exposes two different modes that help with analysis of real-time waits. My 15th post of the month covered the default--lightweight--collection mode. My followup post covered the more extensive full waits collection mode.
Sometimes a query plan and wait information isn't quite enough to diagnose a performance issue. What if the query plan usually works well, but isn't performing properly only in this specific case? Who is Active has a feature to help you figure that out. And what if you need a bit more information on some of the settings that the request is using?
Mining wait information yields some amazing returns. One of the additional pieces of information that you can get is the actual name of the object that's causing a block. Another thing you can see is the exact node within a query plan where a task is currently doing work. You can (and should!) also use waits to figure out whether tempdb is properly configured. There are still more tricks you can play with waits, but they'll have to wait for a future post.
Like wait information, lock data can also be mined. However, there is so much locks information that the real challenge is rendering it in a human-readable manner. Who is Active does that using a special custom XML format. The procedure also helps with another type of blocker analysis, in the form of finding the "lead blocker."
Once you've figured out what information you're interested in, why not set up the output so that you can see the information the way you want to see it? Who is Active helps with this by allowing users to dynamically customize output columns and sort order in a few different ways. And while you could always run Who is Active interactively, that might get a bit dull. Automated data collection is a much nicer methodology in many cases.
Most of the numbers shown by Who is Active are cumulative. But oftentimes it's more interesting to compare data between two snapshots. The procedure can help you do that, using its delta mode.
What fun would a month of Who is Active be without an official release? v11.00 has numerous new features, several of which were perfected this month thanks to feedback I received on the various posts in the series. It's great to have such enthusiastic users! Some of these new features didn't make it into prior posts, and other existing features are a bit hidden. So I did a writeup covering the more important things that you may not have noticed while working with Who is Active.
I finished the month with a discussion on security for slightly tougher situations. I hope that the module signing technique will allow Who is Active to be used in a number of places where security auditing requirements have made things difficult.
And that's that. A month of activity monitoring with Who is Active. Thank you for reading! Next, this text is going to be edited, expanded in places, and put into a much more comprehensive form. Watch your RSS reader for more information.