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Category: Administration

Queueing Event Notifications with Service Broker

Max Vernon ties event notifications to Service Broker:

My previous post shows how to configure an Event Notification to fire whenever a login event occurs. The post uses Service Broker to receive those Event Notifications into a queue, which is then processed by a stored procedure and saved into a standard SQL Server database. This post provides a quick+dirty VB.Net command line monitor that shows how full a Service Broker queue is.

The following code should be pasted into a blank Visual Studio VB.Net console project. It is trivially easy to translate this into C#, but I like VB – what can I say.

Click through for the code. No F# translation from me, however, as I am lazy.

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Tracing a Session with Extended Events

Jason Brimhall shows how you can trace a specific session using Extended Events:

The ability to quickly and easily trace a query is important to database professionals. This script provides one useful alternative to trace a specific spid similar to the method of using the context menu to create the trace within SSMS and Profiler.

This is yet another tool in the ever popular and constantly growing library of Extended Events. Are you still stuck on Profiler? Try one of these articles to help remedy that problem (here and here)

Read on to see how.

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Chaos Engineering with SQL Server

Andrew Pruski is excited about Chaos Engineering:

Chaos Engineering is a practice in which we run experiments against a system to see if it reacts the way we expect it to when it encounters a failure.

We’re not trying to break things here…Chaos Engineering is not breaking things in production.

If I said to my boss that we’re now going to be experiencing an increased amount of outages because, “I AM AN ENGINEER OF CHAOS”, I’d be marched out the front door pretty quickly.

On the plus side, we will know Andrew’s supervillain origin story.

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Interpretability Issues in Monitoring Tools

Brent Ozar explains how it’s hard to explain things without context:

However, outside of that window, you may not have any wait time on CPU at all. If queries are simple enough, and there isn’t enough concurrency, then as we discuss in Mastering Server Tuning, you can end up with SOS_SCHEDULER_YIELD waits with no time attached to them. You wouldn’t notice a CPU problem at all outside of that 8AM window because you don’t have a CPU bottleneck – yet. And to be fair, you probably wouldn’t tune a server in this kind of shape, either.

But when you DO need to tune a server that isn’t running at 100% capacity, picking the right query to tune isn’t just about wait stats: it’s also about which queries you need to be more responsive, and how you need to plan for future load. If your company tries to run a flash sale, and a lot of folks try to check out at the same time, Query T is going to knock your server over. But wait-stats based tools won’t see that coming: they’ll still be focused on Query R, the only one that spends a lot of time waiting on CPU.

Good food for thought.

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Moving tempdb on a SQL Server Instance

Drew Skwiers-Koballa gives us the step-by-step process for moving tempdb from one folder to another on a machine:

Not only can the size of TempDB files be unpredictable (unless the workload is completely predictable or a size limit is placed), but it is full of old Tupperware. That is, if TempDB is destroyed, your SQL Server will create a new one as soon as the service restarts. The whole migration is summarized in these 4 steps:

1. Create a new location for TempDB
2. Use TSQL to change the TempDB file location(s)
3. Restart the SQL Server service during a maintenance window
4. Verify and clean up

This is one of the easier things to move, but it does require server downtime.

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Finding Tables with High Write Frequency

Michael J Swart has an interesting query for us:

You have excessive WRITELOG waits (or HADR_SYNC_COMMIT waits) and among other things, you want to understand where.

Microsoft’s advice Diagnosing Transaction Log Performance Issues and Limits of the Log Manager remains a great resource. They tell you to use perfmon to look at the log bytes flushed/sec counter (in the SQL Server:Databases object) to see which database is being written to so much.

After identifying a database you’re curious about, you may want to drill down further. I wrote about this problem earlier in Tackle WRITELOG Waits Using the Transaction Log and Extended Events. The query I wrote for that post combines results of an extended events session with the transaction log in order to identify which procedures are doing the most writing.

But there are times when you just want a quick and dirty script, and that’s what Michael has for us today.

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Viewing Power BI Audit and Activity Logs

Jeff Pries gives us the rundown on auditing in Power BI:

When using the cloud-based Power BI Service, powerbi.com, every action that is taken while logged into the portal — whether it is viewing or publishing a report, creating a new workspace, or even signing up for a pro trial license, that activity is logged within the Microsoft servers as part of the Office 365 audit logs.

Accessing these logs can be accomplished via a couple of different methods (either through the Office 365 Audit Log functionality using the Office 365 Admin Center or PowerShell cmdlets; or through the new Power BI Activity Log (Power BI Get Activity Events) functionality accessible via a PowerShell cmdlet (Get-PowerBIActivityEvent) and an API). There are a few examples out there already on how to use these commands to access the data (and I have a post on accessing the data using the Power BI API and C# coming out in a few week), but there doesn’t seem to be a lot out there about the data itself, which is what I plan to focus on here.

Read on for more details as well as the structure around a forthcoming application to parse these logs and store them locally in SQL Server.

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Add-ClusterNode Error: Keyset Does Not Exist

Jonathan Kehayias troubleshoots a Windows Server clustering problem:

While working on a video recording for Paul this week I ran into an interesting problem with one of my Windows Server 2016 clusters. While attempting to add a new node to the cluster I ran into an exception calling Add-ClusterNode:

The server ‘SQL2K16-AG03.SQLskillsDemos.com’ could not be added to the cluster.
An error occurred while adding node ‘SQL2K16-AG03.SQLskillsDemos.com’ to cluster ‘SQL2K16-WSFC’.

Keyset does not exist

The windows account I was using was the domain administrator account and I had just recently made modifications that involved the certificate store on this specific VM, so I decided to take a backup of the VMDK and then revert to a snapshot to try again, and this time it worked.  So needless to say I was intrigued as to what I could have done that would be causing this error to happen.

Read on to see what the root cause was and how you can fix it.

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Wait Stats: Necessary but not Sufficient

Greg Gonzalez explains how wait stats are not the only thing you should look at to determine system health:

Waits and Queues has been used as a SQL Server performance tuning methodology since Tom Davidson published the above article as well as the well-known SQL Server 2005 Waits and Queues whitepaper in 2006. When used in combination with resource metrics, waits can be valuable for assessing certain performance characteristics of the workload and aid in steering tuning efforts. Waits data is surfaced by many SQL Server performance monitoring solutions, and I’ve been an advocate of tuning using this methodology since the beginning. The approach was influential in the design of the SQL Sentry performance dashboard, which presents waits flanked by queues (key resource metrics) to deliver a comprehensive view of server performance.

However, some seem to have missed Davidson’s point regarding the importance of resources and rely almost entirely on waits to present a picture of query performance and system health. Waitstats come directly from the SQL Server engine and are easy to consume and categorize. Waiting queries mean waiting applications and users, and no one likes to wait! From a marketing standpoint this is pure gold for a SQL Server monitoring tools vendor – it is easier to evangelize waits analysis as a singular solution for making queries and applications faster than the full story, which is more involved.

Unfortunately, a waits-focused approach to the exclusion of resource analysis can mislead users, and worst-case leave them flying blind. SentryOne team members Kevin Kline and Steve Wright have previously touched on this here and here. In this post I’m going to take a deeper dive into some recent research made possible by Query Store that has shed new light on how deficient waits-focused tuning can truly be.

Interesting research and Greg does a great job of explaining it.

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Finding Events in a Trace

Erin Stellato is on a mission:

Yes…I’m writing a post about SQL Trace…specifically events in a trace. There are still lots of folks that use Profiler and run server-side traces, and when I work with those customers I like to understand how the traces are configured. I want to see what events are in a trace, but I also want to see the filters and if the traces are writing to a file or rowset provider. I wrote this query ages ago and went looking for it today, which means I really should write a post so it’s easier to find

Click through to find out how you can determine which events are included in a particular SQL trace. That way, you can convert them to extended events sessions more easily…

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