05Feb 2018 by Grant Fritchey 3 Comments

Wait Statistics on a Query

SQL Server, SQL Server 2016, SQL Server 2017
Wait statistics are a vital part of understanding what is causing your system to run slowly. Capturing them can be done through a variety of mechanisms from sys.dm_os_wait_stats (use this query for that) to sys.dm_db_wait_stats in Azure SQL Database. Those cover the system and the database, however, what about capturing query wait statistics on a specific query? Query Wait Statistics There was a time when this was actually kind of difficult. However, now we have a lot of different tools to capture query wait statistics. First up, and really, one of the best and easiest ways to deal with this, is to use the wait statistics captured by the Query Store. The only drawback to this method is that it is an aggregation of query wait statistics for the given…
Read More
29Feb 2016 by Grant Fritchey 4 Comments

Wait Statistics in Azure SQL Database

Azure, T-SQL
You need to be aware that you're going to see differences when you're working with Azure SQL Database when it comes to wait statistics. If you're running a v12 Azure SQL Database (and if you're not, go fix it), you can run a query against sys.dm_os_wait_stats. Here's the output for the TOP 10 waits ordered by wait time on one of my databases: Everything you're used to seeing, right? Well... not quite. This is Azure SQL Database. So, let's use sys.dm_db_wait_stats, a DMO that is only available within Azure. This lists waits by database. The TOP 10 here are: You'll notice that these results are wildly different from those above. What we're looking is largely a server versus a database, but not completely. I mean that sys.dm_os_wait_stats is showing the waits for the…
Read More
22Feb 2016 by Grant Fritchey 3 Comments

Why Is The Server Slow?

SQL Server, SQL Server 2016, T-SQL
This is blog post #2 in support of Tim Ford's (b|t) #iwanttohelp, #entrylevel. If you haven't been working in SQL Server for very long, you may not have got this phone call yet, but you will: Hi, yeah, the server is slow. Thanks. Bye. Let's pretend for a moment that you know which server they're referring to (because just finding out that piece of information can be a challenge). Now what? The list of tools and mechanisms within SQL Server for gathering metrics is extremely long: Performance Monitor Dynamic Management Views & Functions System Views Extended Events Trace Events Activity Monitor Data Collector Execution Plans 3rd Party Tools I'm leaving out lots of stuff in that list. So where do you start when you get this phone call? Where is the server slow?…
Read More