Occasionally, when tracking down a performance problem, you have to have information over time on the values of particular sets of performance counters. To track down the more insidious or sporadic problem, it is best to have the data in a SQL Server table, so you can query it. Feodor Georgiev explains the command-line way of doing this.
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Dynamic Management Views and Functions aren't always easy to understand. However, they are the easiest way of finding out which of your stored procedures are using up the most resources. Greg takes the time to explain how and why these DMVs and DMFs get their information. Suddenly, it all gets clearer.… Read more
While we all know that the Query Optimizer uses Indexes to produce better execution plans, we don't all know exactly which indexes will give the best results. Benjamin Nevarez has done the research, and in this sample from his upcoming book, "Inside the SQL Server Query Optimizer", he helps us to understand how the Query Optimizer selects indexes to improve execution plans.… Read more
SQL Server Statistics assist the query optimiser to calculate the best way of running the query. Holger describes every common way that things can go wrong with statistics, and how to put matters right.
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In a perfect world, we should just be able to write queries and leave the RDBMS to decide the perfect strategy to get the data. Until then we have to understand the Query Optimizer and the way it uses distribution statistics. … Read more
Your application code may look neat and clean, and you are using a sound Object-relational Mapper, but when you put the pedal to the metal, you're not getting the performance. The time has come to lift the hood and see what SQL is being generated by the ORM, and what part of your code is causing the bottlenecks. The effect can be spectacular.… Read more
On Ask.SQLServerCentral.com, a group of people interested in experimenting with heavily optimised SQL techniques try them out on a problem, using reasonbly large amounts of data. They aren't so interested in explaining the techniques, so Kathi continues on her mission to explain the lessons learned and the tips that can be derived.… Read more
When you have to routinely collect data from Performance Monitor Counters, it soon becomes easier and more convenient to use PowerShell. SQL Server MVP Laerte Junior was inspired to create a script, and guides us through its useful functions.… Read more
The SQL Speed Freak Challenge is a no-holds-barred competition to find the fastest way in SQL Server to perform a real-life database task. It is the programming equivalent of drag racing, but without the commentary box. Kathi has stepped in to explain what happened with the second challenge and why some SQL ran faster than others.… Read more
By validating the IO path before commissioning the production database system, and performing ongoing validation through page checksums and DBCC checks, you can hopefully avoid data corruption altogether, or at least nip it in the bud. If corruption occurs, then you have to take the right decisions fast to deal with it. Rod Colledge explains how a pessimistic mindset can be an advantag… Read more
Rod Colledge turns his pessimistic mindset to storage systems, and describes the best way to configure the storage systems of SQL Servers for both performance and reliability. Even Rod gets a glint in his eye when he then goes on to describe the dazzling speed of solid-state storage, though he is quick to identify the risks.… Read more
In this sample chapter from his recently released book (co-Authored with Paul Glavich) Chris Farrell gives us a fast overview of performance profiling, memory profiling, profiling tools, and in fact everything we need to know when it comes to profiling our applications. This is a great first step, and The Complete Guide to .NET Performance Testing and Optimization is crammed with even more indispensable knowledge.… Read more
Sometimes, it is a great idea to push away the keyboard when tackling the problems of an ill-performing, complex, query, and take up pencil and paper instead. By drawing a diagram to show of all the tables involved, the joins, the volume of data involved, and the indexes, you'll see more easily the relative efficiency of the possible paths that your query could take through the tables.… Read more
Phil Factor's SQL Speed Phreak challenge is an event where coders battle to produce the fastest code to solve a common reporting problem on large data sets. It isn't that easy on the spectators, since the programmers don't score extra points for commenting their code. Mercifully, Kathi is on hand to explain some of the TSQL coding secrets that go to producing blistering performance. … Read more
A great deal can be gleaned from the use of the STATISTICS IO and the execution plan, when you are checking that a query is performing properly. Josef Richberg, the current holder of the 'Exceptional DBA' award, explains how an apparently draconian IT policy turns out to be a useful ways of ensuring that Stored Procedures are carefully checked for performance before they are released… Read more
The Query Optimizer gets it right most of the time, but occasionally it chooses a plan that isn't the best possible. You can give the Query Optimiser a better idea by using Table, Join and Query hints. These come with a risk: Any choices you force on the Optimizer by using hints can turn out to be entirely wrong as the database changes with the addition of data over time. Grant Fritchey, in a chapter from his highly acclaimed book, explains further.
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In this sample chapter from his upcoming book, Paul Glavich explains performance metrics and walks us through the steps needed to establish meaningful performance targets. He covers many metrics such as "time to first byte" and explains why you should add some contingency into your estimated performance requirements.… Read more
Laerte recently experienced an I/O nightmare, which, as a happy accident, gave him an opportunity to test out the 'Missing Indexes' DMVs and see if they were up to scratch. He solved his problems, ran a few tests to get a feel for how well the DMVs performed, and was very impressed. So much so, that he is sharing his findings with us.… Read more
Why is my query running slow? Why isn't my index getting used? In order to answer these questions, you have to ask the same return question in each case: have you looked at the execution plan? Grant Fritchey provides the only dedicated and detailed guide to this essential topic. Download the eBook.… Read more
