Finding Failed Queries

Andrew Pruski shows how to use extended events to find queries with errors:

What this is going to do is create an extended event that will automatically startup when the SQL instance starts and capture all errors recorded that have a severity level greater than 10.

Full documentation on severity levels can be found here but levels 1 through 10 are really just information and you don’t need to worry about them.

I’ve also added in some extra information in the ACTION section (for bits and bobs that aren’t automatically included) and have set the maximum number of files that can be generated to 10, each with a max size of 5MB.

Check it out.  At one point, I had created a small WPF application to show me errors that extended events caught.  It completely freaked out a developer when I IM’d him and told him how to fix the query he’d just run from the privacy of his cube, with me nowhere to be seen.

Extended Event Handler Application

Dave Mason whipped up an application to track when a particular extended event fires:

Event Responses: when an event is handled, specify how you want to respond to it. In the “Event Responses” section, there are two options: play a system sound or send email (you must choose at least one option). Pick the system sound desired and/or enter an email address.

Dave has made the source code available as well so you can extend the functionality.

Finding Database Growth Events

Arun Sirpal has an Extended Events session which tracks growth events on a database file:

A quick post that is hopefully useful, I wanted a quick way to find the time, size of the database file size change and who caused it.

I went down the extended events route using sqlserver.database_file_size_change event. By the way I am no Extended Events expert, I write a lot via trial and error I am trying to wean off Profiler.

Read on for the script as well as a query which shreds the XML and returns a result set.

Stop Profiling

Wayne Sheffield concludes his two-part series on converting a trace to use Extended Events:

This query extracts the data from XE file target. It also calculates the end date, and displays both the internal and user-friendly names for the resource_type and mode columns – the internal values are what the trace was returning.

For a quick recap: in Part 1, you learned how to convert an existing trace into an XE session, identifying the columns and stepping through the GUI for creating the XE session. In part 2 you learned how to query both the trace and XE file target outputs, and then compared the two outputs and learned that all of the data in the trace output is available in the XE output.

Read the whole thing.

Breakpoint Extended Event

Arun Sirpal is a dangerous man of mystery and danger, but mostly danger:

I did a dangerous thing, and I want to make sure that YOU DO NOT do the same.

I was creating a couple of extended events sessions and was playing around with some actions. I ended up with the following code where I was after a guy called Shane:

The probability that you intend to set a breakpoint in SQL Server via Extended Event is quite low (low enough that if you’re doing it, you should already know what you’re doing), but click through to see exactly what damage you can do.

Getting Off Of Profiler, A Twelve-Step Program

Wayne Sheffield has a blast from the past, repeating an old T-SQL Tuesday to show how to use Extended Events:

Now that you have this XE session scripted out, it can be easily installed on multiple servers. If you encounter a deadlock problem, you can easily start the XE session and let it run to trap your deadlocks. They will be persisted to a file dedicated for the deadlocks. You can use my Deadlock Shredder script at http://bit.ly/ShredDL to read the deadlocks from the file and shred the deadlock XML into a tabular output.

Note that the default system_health XE session also captures deadlocks. I like to have a dedicated session for just deadlocks. As lightweight as XE is, sometimes it may benefit a server to turn off the system_health session. Additionally, Jonathan Kehayias has a script that will take a running trace and completely script out an XE session for it. This script can be found at https://www.sqlskills.com/blogs/jonathan/converting-sql-trace-to-extended-events-in-sql-server-2012/. Even though this script is available, I like to figure things out for myself so that I can learn what is actually going on.

Extended Events are extremely useful for administrators, typically with a fraction of the overhead cost of  server-side (much less Profiler) traces.

Dark Queries

Michael Swart helps root out queries which get recompiled frequently and so won’t be in the cache:

Some of my favorite monitoring solutions rely on the cached queries:

but some queries will fall out of cache or don’t ever make it into cache. Those are the dark queries I’m interested in today. Today let’s look at query recompiles to shed light on some of those dark queries that maybe we’re not measuring.

By the way, if you’re using SQL Server 2016’s query store then this post isn’t for you because Query Store is awesome. Query Store doesn’t rely on the cache. It captures all activity and stores queries separately – Truth in advertising!

Click through for an Extended Event session which looks for recompilation.

SSAS Extended Events

Eugene Polonichko shows how to use Extended Events with SQL Server Analysis Services:

Cubes require frequent monitoring since their productivity decreases quite often (slowdowns during query building, processing time increment). To find out the reason of decrease, we need to monitor our system. For this, we use SQL Server Profiler. However, Microsoft is planning to exclude this SQL tracing tool in subsequent versions. The main disadvantage of the tool is resource intensity, and it should be run on a production server carefully, since it may cause a critical system productivity loss.

Thus, Extended Events is a general event-handling system for server systems. This system supports the correlation of data from SQL Server which allows getting SQL Server state events.

If you’re already familiar with relational engine XEs, this isn’t much of a stretch.

Replication Extended Events

Drew Furgiuele goes hunting for the most dangerous creature of all, replication-related extended events:

Extended events are great; they have all the goodness of profiler except you don’t use profiler. Win/win! More to the point, extended events let you quickly and easily view, sort, and aggregate events that occur on your instances. They also have powerful filters (really, a “where” clause) to limit noise. You have way more control over what you monitor, how you store the data, and how you view and use it. This makes them perfect use to track replicated transactions, since we want to measure at both an individual level and the aggregate.

I fired up management studio and went to “New Session” looking for some replication event goodness and I found…

… nothing. I tried looking for events that had even parts of the name replication in it. No such thing, apparently.

This doesn’t deter Drew and he ends up building some interesting events to infer the correct answers.

Retaining system_health Metrics

Taiob Ali looks at the system_health Extended Events session:

What this article does not tell you is your individual file size is 5 MB and number of maximum rollover file is 4. Meaning you will only get 20 MB of data. Once that limit is reached your older data is lost and there is no way to recover.

Often time you have an issue with the application pointing to SQL Server and you want to diagnose the problem with system_health files. You find that files already rolled over and information you are looking for is not available. I will explain how you can solve this problem and retain system_health session files for longer period.

Read on for the solution.

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