Announcing the comprehensive SQL Server Wait Types and Latch Classes Library

It’s finally ready!

For the last two years, I’ve been working on-and-off on a new community resource. It was postponed during 2015 while I mentored 50+ people, but this year I’ve had a bunch of time to work on it.

I present to the community a comprehensive library of all wait types and latch classes that have existed since SQL Server 2005 (yes, it includes 2016 waits and latches).

The idea is that over time, this website will have the following information about all wait types and latch classes:

  • What they mean
  • When they were added
  • How they map into Extended Events (complete for all entries already)
  • Troubleshooting information
  • Example call stacks of where they occur inside SQL Server
  • Email link for feedback and questions

As of today, I have complete information for more than 225 common wait types (897 entries in the library) and 26 common latch classes (185 entries in the library), and I’m adding more information constantly.

If there’s one that I haven’t done yet, and you’re really interested in it, click the email link on the page to let me know. Also, if you’ve seen something be a bottleneck that I haven’t, let me know so I can update the relevant page too.

I’m doing this because there is so little information about waits and latches available online and I know that people are constantly searching for information about them. This is very much a labor of love for me as wait statistics are now my favorite area to teach.

Waiting until it’s complete isn’t feasible, so it’s open and available for use now!

Check it out at and, or jump to some examples PAGELATCH_EX, SOS_SCHEDULER_YIELD, WRITELOG, CXPACKET.


22 thoughts on “Announcing the comprehensive SQL Server Wait Types and Latch Classes Library

  1. Thank you so much. I was really excited to hear this when you announced it in class, and it is going to be a well utilized tool.

  2. Thank you so much for your efforts in compiling a vast topic and sharing it for public use, Paul. It really helps!

  3. Thank you so much Paul for giving up your time to provide the level of documentation that Microsoft should have provided!

  4. Much appreciated! Certainly now SQL Server started to expose ‘wait events’ per session, there’s no excuse not to use them anymore.

  5. Paul, thank you to you and your team for the efforts in putting together this wonderful resource.

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