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Ten Common Threats to Execution Plan Quality

The quality of an execution plan is highly dependent on the accuracy of the estimated number of rows output by each plan operator. If the estimated number of rows is significantly skewed from the actual number of rows, this can have a significant impact on the quality of a query's execution plan. Poor plan quality can be responsible for excessive I/O, inflated CPU, memory pressure, decreased throughput and reduced overall concurrency.

  ◆  November 13, 2012
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The Zombie PerfMon Counters That Never Die!

One of the things that's simultaneously great and horrible about the Internet is that, once something gets posted out in the ether, it basically never goes away. (Some day, politicians will realize this. We can easily fact check their consistency.) Because of longevity of content posted to the Internet, a lot of performance tuning topics become "zombies." We shoot 'em dead, but they keep coming back!

  ◆  October 17, 2012
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Configuring a Dedicated Network for Availability Group Communication

SQL Server 2012 AlwaysOn Availability Groups require a database mirroring endpoint for each SQL Server instance that will be hosting an availability group replica and/or database mirroring session. This SQL Server instance endpoint is then shared by one or more availability group replicas and/or database mirroring sessions and is the mechanism for communication between the primary replica and the associated secondary replicas.

Depending on the data modification workloads on the primary replica, the availability group messaging throughput requirements can be non-trivial. This activity is also sensitive to traffic from concurrent non-availability group activity. If throughput is suffering due to degraded bandwidth and concurrent traffic, you may consider isolating the availability group traffic to its own dedicated network adapter for each SQL Server instance hosting an availability replica. This post will describe this process and also briefly describe what you might expect to see in a degraded throughput scenario.

  ◆  October 11, 2012
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Checking if a non-LOB column needs to be updated

Occasionally I see people try to "optimize" their update statements to avoid writing the same value to a particular column. My understanding has always been that if you're going to update a row, assuming all of the values are in-row, the costs of locking the row are much higher than the incremental cost of updating one, two or all columns in that row.

  ◆  October 3, 2012
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Hit-Highlighting in Full-Text Search

Hit-highlighting is a feature that many people wish SQL Server's Full-Text Search would support natively. This is where you can return the entire document (or an excerpt) and point out the words or phrases that helped match that document to the search. Doing so in an efficient and accurate manner is no easy task, as I found out first hand.

  ◆  September 24, 2012
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