Collecting Deadlock Information

Kendra Little has scripts to collect deadlock graph information using extended events or a server-side trace:

Choose the script that works for you. You can:

  1. Use a simple Extended Events trace to get deadlock graphs via the sqlserver.xml_deadlock_report event

  2. Use a Server Side SQL Trace to get deadlock graphs (for older versions of SQL Server, or people who like SQL Trace)

  3. Use a (much more verbose) Extended Events trace to get errors, completed statements, and deadlock graphs. You only need something like this if the input buffer showing in the deadlock graph isn’t enough, and you need to collect the other statements involved in the transactions. You do this by matching the transaction id for statements to the xactid for each item in the Blocked Process Report. Warning, this can generate a lot of events and slow performance.

I’d default to script #1 and look at #3 in extreme scenarios.

Blocked Process Report

Kendra Little has a few Github gists showing how to configure the blocked process report:

I wanted a friendly way to share code to configure and manage the Blocked Process Report, so I’ve created a gist on GitHub sharing TSQL that:

  • Enables the Blocked Process Report (BPR)

  • Collects the BPR with an Extended Events trace

  • Collects the BPR using a Server Side SQL Trace (in case you don’t care XEvents or are running an older version of SQL Server)

  • Lists out the Extended Events and SQL Traces you have running, and gives you code to stop and delete traces if you wish

Click through for the code.

Figuring Out Who Dropped That Database

Kevin Hill reads the default trace to figure out who dropped a database:

We have a staging server that has a database for each client that we can test on before working in their production databases.   Recently one has gone missing a few times…but nobody will own up to it.

If you want to set up an extended event to capture this information to disk separately, Jason Brimhall has you covered.

Backing Up Extended Event Logs

Wayne Sheffield reminds us that backups aren’t just for databases:

So how does this talk of AGs pertain to this T-SQL Tuesday topic? It should be pretty obvious – we need to periodically grab all of the .xel files generated by the cluster, and move them to a different directory, with a different retention policy. Yup… we need to back up these files. Sometimes, we need to be backing up things other than the databases themselves.

I created a PowerShell script that takes a few parameters, then moves the files from the source directory to the destination directory. And then it deletes files from the destination directory that are over x days old.

Wayne goes into more detail, including permissions required to run the script.

Discovering Deprecated Functionality

Jason Brimhall shows how to see if you’re using deprecated functionality in SQL Server:

Right here would be a good time to point out that your mileage may vary. Some items that are deprecated are more painful than others. Some may be deprecated and may have been on the list for 10+ years at this point. The point is, know your environment and then use good judgement to determine which items in your results need the most attention to fix and update. Why? Well, things really may break especially if you are looking to upgrade to a new version of SQL Server. Just because an item is still available in your current edition, that does not ensure it will still be available in a future release of SQL Server.

Now for the juicy stuff. As I mentioned, finding when and where a deprecated feature or syntax is employed, there are a couple of neat little events within Extended Events that can help to track each time a deprecated feature is accessed or employed. How do we do that? Use the deprecation_announcement and deprecation_final_support events. To help create sessions to track these events, I have the following script to create an “audit” session to do exactly that.

Click through for Extended Event scripts and demo code.

Finding Long-Running Queries

Peter Schott has an Extended Event to find long-running queries:

This has been something I’ve wanted to investigate for a while now. I’ve know you could use Profiler and set up server-side traces to capture long-running events, but was curious how to do the same with Extended Events. I then came across this post from Pinal Dave ( b | t ) that pointed me in the right direction. I followed along with the guidelines he was suggesting and was having trouble finding the “Duration” filter. Turns out I had a bit too much selected in my filtering options or perhaps the Wizard was giving me fits seeing it, but I eventually selected just the Batch Completed or RPC Completed events to see and set the Duration filter. The one change that I’d make from Dave’s script is to set the duration to 500,000 because Duration in SQL 2012 is in microseconds, not milliseconds. I also want queries longer than 5 seconds to start.

Click through for the script.

Analysis Services Locking And Blocking

Bill Anton shows how to figure out if your Analysis Services performance problem is due to locks:

This past weekend, after one of my presentations on Analysis Services at SQL Saturday 520, an attendee described a performance issue in his environment that he thought could be related to locking and blocking and asked if there was a way to confirm if this was the cause. The short answer is yes, absolutely!

While I wouldn’t say this is a common issue across *all* analysis services environments, it’s definitely common amongst the subset of analysis services environments that do intra-day processing – which is when the SSAS database is being processed during hours of the day when users might be simultaneously querying it.

This is a very interesting article.  I’d never thought about SSAS taking locks, but it makes perfect sense.

Error Handling Extended Event

Dave Mason shows how to use an Extended Event to capture error data:

Here’s an example for DBCC CHECKDB on a corrupt database. Remember from the last post that in this scenario, control never passes to the CATCH block. So we’ll need to check the Event Session data after END CATCH. You can also run this as a single batch in SSMS, but you’ll need a corrupt database to get similar results. As before, replace “2016” with your SPID.

There are a lot of working parts to this, so read the scripts carefully if you’re interested in implementing something similar yourself.

XE Default Sessions

Jason Brimhall goes into the various Extended Events default sessions:

With the release of SQL Server 2016 there is another default session that gets installed. This session is probably the most difficult to find. This is a private hidden session when it is installed. In addition, it is not present by default with SQL 2016 RTM but it was present by default with various CTP versions. The session is specific to the new stretch feature and is called rdaxesession.

Breaking down this particular session reveals pretty easily what feature the session is designed to support. The name rdaxesession breaks down to the following: rda = remote data archive, and then the rest is self explanatory. If I investigate the metadata for the session I will discover that the following events are traced in the session:

Jason also has an earlier blog post about the default sessions I tend to use, like system health.

Extended Events Audit

Steve Jones creates an audit with Extended Events:

The third part of the invitation was to write this. I covered what I did, and some of what I learned. I’ll add a bit more here.

I certainly was clumsy working with XE, and despite working my way through the course, I realize I have a lot of learning to do in order to become more familiar with how to use XE. While I got a basic session going, depending on when I started it and what I was experimenting with, I sometimes found myself with events that never went away, such as a commit or rollback with no corresponding opening transaction.

This T-SQL Tuesday was a bit broader in scope, so it has been interesting watching people respond.

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