When does physical reads include read-ahead reads in SQL Server?
SQL Server has more than one way to pull pages in from disk for your queries. SQL Server can do a physical read of an 8KB page, or an extent of 8 of those 8KB pages.
Top 5 Misleading SQL Server Performance Counters
Perfmon counters are an excellent tool for monitoring and sometimes troubleshooting Microsoft SQL Server. But some counters can get you into trouble, because they don’t mean what many people think. Learn what to look out for in the world of widely-used perfmon counters.
Register for Upcoming Free Webcasts on Indexes, Stats Maintenance, Query Tuning, and More
I’ve got a whole bunch of free, live webcasts scheduled on SQL Server training! I’d love for you to join me for these sessions.
Database Mirroring Counters Missing from Perfmon?
Collecting perfmon counters from SQL Server databases where you are using database mirroring is a little tricky
The counters won’t behave “normally” until after you set up mirroring for a database.
Why I am Inspired to Start Up Live Webcasts Again
For a while now, I’ve been indulging in what feels like a huge guilty pleasure: an almost meeting-free existence. I’ve been living life scheduled on my own terms. I commit to appointments for workouts, volunteering, haircuts, and medical appointments, but not much else. I’ve been publishing pre-recorded videos and online courses which I can make whenever it feels right.
Finding Queries that Cause Wait Stats in SQL Server
You’ve got some troubling wait stats in SQL Server. How can you tell which queries are causing those waits?
Learn the pros and cons of different techniques to track down the cause of both common and tricky waits in SQL Server, including CXPACKET, PAGEIOLATCH, LCK, RESOURCE_SEMAPHORE, and THREADPOOL waits.
When a Nonclustered Index and Statistics Make a Query Slower
Nonclustered indexes are awesome in SQL Server: they can get you huge performance gains.
But we can’t always create the perfect index for every query. And sometimes when SQL Server finds an index that isn’t quite perfect and decides to use it, it might make your query slower instead of faster.
Removing Query Hints with Plan Guides (Dear SQL DBA Episode 43)
If you need to add, remove, or replace hints from ad-hoc queries where you can’t change the code, plan guides can help. See a demo of removing a query hint from parameterized TSQL run from an application, and get tips on how to make your plan guides work in SQL Server.
Perfmon: Batch Requests/sec counts whole batches, not statements
The name of the “SQL Statistics \ Batch Requests/sec” counter is confusing: exactly what is a request? The request is the WHOLE batch. See a demo of this counter in this quick 5 minute video.
Batch Mode Hacks for Rowstore Queries in SQL Server
What’s batch mode? Batch mode was introduced as a way to help SQL Server process data from columnstore indexes faster. The whole idea with columnstore is that you pull big compressed sets of rows out for aggregation or other operations in big chunks. Batch mode is a way that operators can work on a “batch” of up to 900 values at a time, instead of working on individual rows. Batch mode can reduce the overhead of metadata and make more efficient use of your CPUs.