Press "Enter" to skip to content

Category: Administration

sample_ms in sys.dm_io_virtual_file_stats and Data Types

Published 2021-04-22 by Kevin Feasel

Paul Randal points out an interesting bug:

A prior student emailed me yesterday about some strange behavior of the sample_ms column in sys.dm_io_virtual_file_stats. It’s supposed to be the number of milliseconds since the SQL Server instance has been started. He has a SQL Server 2016 instance that’s been running since August 2019, and it shows the following:

– ms_ticks from sys.dm_os_sys_info: 51915112684 (which works out to be August 28, 2019)

– sample_ms from sys.dm_io_virtual_file_stats: 375504432 (which works out to be about 4.5 days)

Read on to get a determination and an alternative in case you’re using that field.

Comments closed

Unkillable Threads

Published 2021-04-21 by Kevin Feasel

Paul Randal gives us a supervillain origin story:

While I was teaching IEPTO2 last week, I was discussing why sometimes a thread cannot be terminated using the KILL command, and thought it would make a great topic for a post.

Some of you have likely seen a phenomenon called a non-yielding scheduler. This is where a thread is using the processor and doesn’t voluntarily yield after using more than the thread quantum (4 milliseconds, unchangeable). There’s a background task called the scheduler monitor that checks that progress is being made on the various schedulers inside SQL Server and issues a warning if it finds a problem.

Read on to learn more about how this can happen and what it means for you.

Comments closed

Changing SQL Server to Use a Static, Non-Standard Port

Published 2021-04-20 by Kevin Feasel

Jack Vamvas has a cmdlet for us:

Question: I have an  SQL Server Instance – currently configured with a Dynamic Port. I’d like to change the setting from a Dynamic port configuration to a Static port configuration , using Powershell.

I want to change to a static port as we need to set up some Firewall rules , and using a static port will be much easier

How can this be done?

Click through for the answer.

Comments closed

Extended Events in Azure SQL Database

Published 2021-04-20 by Kevin Feasel

Grant Fritchey compares and contrasts extended events on-premises to extended events in Azure SQL Database:

I have long advocated for the use of Extended Events. I’ve been posting all sorts of blog posts on how to implement them, how they present unique opportunities for new and interesting data, and how they do so much more than the old trace events, yet, put less of a load on the system. All of that is true, until we hit Azure SQL Database.

Now, don’t get me wrong, Extended Events are still awesome, amazing and wonderful. It’s just that, Azure SQL Database is going to force us to hop through a few hoops. I want to be up front with these… I’m trying to find the right word here, challenges? Maybe. Frustrations? Yeah, kind of. Limitations? Again, sort of, but not quite. We’ll settle on as neutral a term as possible: differences. For the moment.

Read on for the first part in an ongoing series.

Comments closed

Removing a Node from a Hadoop Cluster

Published 2021-04-19 by Kevin Feasel

The Hadoop in Real World team shows us the proper way to remove a node from a Hadoop cluster:

This post will list out the steps to properly remove a node from a Hadoop cluster. It is not advisable to just shut down the node abruptly.

Node exclusions should be properly recorded in a file that is referred to by the property dfs.hosts.exclude. This property doesn’t have default value so in the absence of a file location and a file, the Hadoop cluster will not exclude any nodes.

Read on for more information, including what happens if you simply turn off the node.

Comments closed

Capturing Deadlocks with the system_health Extended Event

Published 2021-04-19 by Kevin Feasel

Jack Vamvas is hunting deadlocks:

An application using SQL Server as the database backend was experiencing some application rollbacks. I decided to investigate the SQL Server to identify any errors which could be correlated to the application timeouts experienced by the users. 

I started reviewing the errors in the Extended Events system health logs, which are normally running by default on a SQL Server. They have a ton of useful information . I noticed a steady stream of deadlocks . This is the code used to create a permanent table to store the deadlock details , for review by the application team. 

Click through for the script.

Comments closed

Using AD Authentication on Linux when Connecting to SQL Server

Published 2021-04-16 by Kevin Feasel

Daniel Hutmacher shares some hard-earned wisdom:

I’m a complete beginner at Linux, so I should preface this post with the fact that these are my humble notes after hours of pulling my hair. It’s not really a fully-fledged how-to article, and there are lot of things I’m not covering. But I figured it may help someone out there at some point.

Also, different Linux distros and versions will behave differently, so your mileage will most likely vary.

For the purposes of this post, I’m on Red Hat Enterprise 8.3.

Note that this is using a Linux-based client, rather than talking about SQL Server on Linux.

Comments closed

Finding and Clearing the Recycle Bin with Powershell

Published 2021-04-12 by Kevin Feasel

Jack Vamvas answers a question:

I use Powershell extensively to manage SQL Server and the Windows OS. A common problem is to identify location of the  Windows Recycle Bin and clear the contents down – particuarly if there is a space issue. 

How can I locate the Windows Recycle Bin and clear it down?

Read on for the Powershell v5 solution as well as the solution which works for earlier versions.

Comments closed

IDENTITY Overflow in SSIS

Published 2021-04-08 by Kevin Feasel

Alex Stuart hits a weird error:

Conversion/overflow errors aren’t that unusual – normally a data flow broken by some unexpected data (“no, there’s no chance that field would ever have a character in it”), or perhaps a column hitting max size (“INT will be enough for years, like, 5 years. I’ll have left the company by then”)

But that wasn’t the case here – the package and user tables involved were checked by the dev team and there was no possible overflow. I’d checked system databases for maxed-out identity columns and found nothing. Heads were scratched.

Read on for the post-head-scratch answer.

Comments closed