Press "Enter" to skip to content

Category: Administration

Dealing with Non-Yielding Schedulers

Published 2021-08-26 by Kevin Feasel

Sean Gallardy breaks up the party:

One of the most common items that will cause a memory dump in SQL Server is a non-yielding scheduler (generally referred to as NYS). What the heck does that mean? Why would it cause a memory dump? Is there anything that can be investigated? Good questions, let’s take a look.

Read on to learn what these are, why they’re not something you want to deal with on a regular basis, and how you can get more information on what happened out of a dump file. Which is also going to be helpful for Microsoft staff to diagnose and correct the underlying issue (if possible).

Comments closed

Sending an E-Mail upon Database Creation

Published 2021-08-24 by Kevin Feasel

Thomas Williams has a job for SQL Server:

As part of commissioning a SQL Server, I create a server trigger to send an e-mail when a new database is created (adapted from https://www.mssqltips.com/sqlservertip/2864/email-alerts-when-new-databases-are-created-in-sql-server/), and a SQL Agent alert which e-mails when a database is restored (inspired by Jeremy Dearduff’s comment at https://www.brentozar.com/archive/2017/06/tracking-restores-hard/#comment-2446362).

After receiving the e-mail I can follow up and include the database in an inventory. See below for the trigger and alert scripts – feel free to use these as a basis for your own monitoring and inventory.

Click through for the script, as well as an important disclaimer.

Comments closed

Changing the Slow Query Log Threshold in RDS

Published 2021-08-20 by Kevin Feasel

John McCormack wants to know about those slow queries:

The slow query log will record all queries which are above the threshold level. The default value is 10 (seconds) but you can set it higher or lower depending on your requirements. It is useful for finding slow queries and allows you to pick out candidates for tuning.

If you set the threshold too low, it can increase I/O overhead on your instance and use a lot of valuable disk space. If you set it too high, it might not capture enough useful information.

This is a setting in AWS Relational Database Services and mimics functionality in MySQL

Comments closed

Projecting Disk Space Available

Published 2021-08-20 by Kevin Feasel

Constantine Kokkinos predicts the future:

The first question I wanted to model out was a bigger issue with on-premises databases – when are we going to run out of storage?

Back in the day I’d cheat with msdb backups, comparing compressed sized to actuals, and moving on. However I don’t have a historical reference for Stack Overflow… so what can I do?

Taking a look at the tables we see a commonality in many tables – CreationDate! It looks like the rows faithfully are stamped when they are created.

Constantine does at the end hit on something we tend to forget: most operations in life aren’t quite linear. We often get lucky in that certain stretches are close enough to be linear that we can model them that way, but even in this dataset, you can see the effects of polynomial growth slowly build up. Still, this is a good way of taking us through what an analysis and projection can look like.

Comments closed

When Did That SQL Server Start?

Published 2021-08-20 by Kevin Feasel

Chad Callihan breaks out the stopwatch:

When you are troubleshooting query performance, it’s important to consider when SQL Server last restarted. Each time SQL Server restarts, buffer pool and plan cache get wiped out. This can play a big part in how you approach an issue.

You want to know how much history you have to work with. Not seeing much data in plan cache? Maybe SQL Server restarted recently. Parameter sniffing issues that you were seeing earlier today are now suddenly “fixed?” SQL Server could have restarted between then and now. Let’s take a quick look a few ways to review how long SQL Server has been up and running.

Click through for several techniques. I’ve always checked the tempdb startup time in sys.databases, myself, but that’s not the only way.

Comments closed

Fixing Hadoop Namenodes in Safe Mode

Published 2021-08-16 by Kevin Feasel

The Hadoop in Real World team doesn’t need to play it safe:

When namenode is started or restarted, namenode will be in safemode for a period of time. At this time you will not be able to use your Hadoop cluster fully. Write operations to HDFS will fail and because of that your MapReduce jobs will also fail.

Read on for other reasons why the namenode might be stuck in safe mode and what you can do to fix it.

Comments closed

Using the DAC from SSMS

Published 2021-08-16 by Kevin Feasel

Chad Callihan shows how you can configure the dedicated administrator connection and connect to it via SSMS in a time of need:

Have you heard of SQL Server’s dedicated administrator connection? The dedicated administrator connection (DAC) can come in handy in an emergency scenario so you should have it enabled and know how to use it…just in case. I haven’t needed it too often in my career but it was helpful in instances when SQL Server wasn’t being very responsive. If there are problems connecting to a server, the DAC can be used to connect and troubleshoot issues.

Read on to learn more.

Comments closed

Troubleshooting a Slow Restore

Published 2021-08-09 by Kevin Feasel

Sean Gallardy performs corporate dentistry:

This came with very little to no data available, and to be quite honest, saying “slow restore” doesn’t really mean much. The initial analysis needs to be an actual set of concrete data that describes the issue, what is normal, and what outliers, if any, exist. Since we have none, we can’t even start to analyze anything, so we need to clarify the problem statement and understand a little more about the issue.

This is an interesting dive into the problem and a good example of how to work with “We won’t let you see/do that” as a consultant. Incidentally, if you haven’t heard of WPR, that comes with the Windows Performance Toolkit.

Comments closed

Monitoring SQL Server on Linux with Telegraf, InfluxDB, and Grafana

Published 2021-08-09 by Kevin Feasel

Amit Khandelwal extends a solution for SQL Server on Windows:

In this blog, we will look at how we configure near real-time monitoring of SQL Server on Linux and containers with the Telegraf-InfluxDB and Grafana stack. This is built on similar lines to Azure SQLDB and Managed Instance solutions already published by my colleague Denzil Ribeiro. You can refer to the above blogs to know more about Telegraf, InfluxDB and Grafana. 

Click through for the quick version, and then the step-by-step process.

Comments closed

Updating SQL Server Container Memory Limits

Published 2021-08-09 by Kevin Feasel

Andrew Pruski doesn’t have time to restart containers:

When running multiple SQL Server containers on a Docker host we should always be setting CPU and Memory limits for each container (see the flags for memory and cpus here). This helps prevent the whole noisy neighbour situation, where one container takes all the host’s resources and staves the other containers.

But what if we forget to set those limits? Well, no worries…we can update them on the fly!

Click through to see how you can change the memory limits on a running container.

Comments closed