The following table summarizes the results from my last two blog entries, showing the CPU time used when performing 5 million clustered index seeks: In test 1, making the clustered index unique improved performance by around 40%. In test 2, making the same change reduced performance by around 70% (on 64-bit systems – more on that later).  ...

Back when my day-to-day duties included database administration work and enterprise architecture, I became rather obsessed with the idea of operational excellence. I read everything I could on the topic. I made a list of favorites, which became somewhat shabby over time, as I dog-eared important pages and scribbled notes in the margins. ...

Remote Desktop Services Component Architecture Poster Grab your own poster! A visual guide to key Remote Desktop Services technologies in Windows Server 2008R2     Virtually Free Get the latest update rollup package for the Hyper-V role in Windows Server 2008 R2 and be sure to bookmark the Windows Virtualization ...

You probably already know that it’s important to be aware of data types when writing queries, and that implicit conversions between types can lead to poor query performance.  Some people have gone so far as to write scripts to search the plan cache for CONVERT_IMPLICIT elements, and others routinely inspect plans for that type of thing when ...

I profiled Adam Machanic's (blog | twitter) excellent stored procedure, SP_WHOISACTIVE, back in August of 2010 in my monthly SQLMag column, Tool Time.  Adam has been diligent about maintaining the tool and adding new features. Read the details on my SQLMag Tool Time column (here - ...

Last week, I wrote about logging for index rebuild operations.  I wanted to publish the result of that testing as soon as I could, because that dealt with a specific question I was trying to answer. However, I actually started out my testing by looking at the logging that was done for a different operation, and ended up generating some new ...

This blog post was inspired by a question from a future student. Someone who was already booked for my SQL Server Internals class in June asked for some information on a current problem he was having with transaction log writes causing excessive wait times during index rebuild operations when run in ONLINE mode. He wanted to know if switching to ...

You might have noticed that January was a quiet blogging month for me.  Part of the reason was that I was working on a series of articles for Simple Talk, examining how parallel query execution really works.  The first part is published today ...

There is much more to query tuning than reducing logical reads and adding covering nonclustered indexes.  Query tuning is not complete as soon as the query returns results quickly in the development or test environments.  In production, your query will compete for memory, CPU, locks, I/O and other resources on the server.  Today’s ...

Is it possible to see LOB (large object) logical reads from STATISTICS IO output on a table with no LOB columns? I was asked this question today by someone who had spent a good fraction of their afternoon trying to work out why this was occurring – even going so far as to re-run DBCC CHECKDB to see if any corruption had taken place.  The ...