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Category: Administration

SQL Server Configuration Settings Requiring Restarts

Published 2021-03-04 by Kevin Feasel

Randolph West enumerates configuration settings which do (or do not) require a restart of the SQL Server database engine:

SQL Server is a complex beast, with many configuration options that can range from recommended to completely avoided.

Since the release of SQL Server 2016, several options that were recommended post-install have been rolled into the default installation options and no longer need to be done, and similar changes were made with SQL Server 2017. Even so, there are configuration changes we data professionals need to make after installation, during maintenance windows, and sometimes even during operating hours, so here’s a handy list of changes that do and don’t require a restart of your operating system or SQL Server instance.

As Randolph mentions, this set is not conclusive. For example, enabling PolyBase requires a restart of the database engine. I believe enabling ML Services technically does not, though I do out of caution because the back of my mind remembers something weird about the service’s behavior if you don’t restart the database engine, but p > 0 my brain made up the whole thing.

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Combining SendTo and Powershell

Published 2021-03-02 by Kevin Feasel

Mark Wilkinson shares a script with us:

If you are not familiar, SendTo options are those available when you right click on a file/folder in file explorer and select the Send To option in the menu. When you use this option, the currently selected files/folders are passed to the SendTo shortcut as a space delimited list of files and folders. This is important to know so you better understand what needs to be done to read that list.

I can confirm that this works well for deploying script out, especially when they need to go to multiple servers or multiple databases on servers. That functionality takes a bit more effort to write, but combine Mark’s code with Jess’s and you are well on your way.

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Tracking Log Rolling in SQL Server

Published 2021-03-02 by Kevin Feasel

Andrea Allred wants to figure out how frequently logs roll over:

In January, the awesome Tim Radney (b|t) talked to the Utah user group about best practices. One that he mentioned was rolling over your error logs everyday and keeping 35 logs (a month plus 3 reboots). I loved this idea and implemented it using what I had done here and adding it to an agent job.

Then I realized we didn’t have any alerts on if our logs were rolling too much. Way back in my career, it used to be something that I would watch and it could mean someone was trying to hack your system and cover their tracks by rolling your logs over a bunch. I fought so much with figuring how to tell if my logs are rolling over, I had to save it for the future.

Click through for a T-SQL solution to the problem.

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Executing a Folder of SQL Scripts against SQL Server

Published 2021-03-02 by Kevin Feasel

Jess Pomfret has a quick Powershell snippet for us:

Another week and another useful dbatools snippet for you today.  Last week at work I was given a folder of 1,500 scripts – each containing a create table statement. Can you imagine having to open each file in Management Studio to be able to execute it? Thank goodness we have PowerShell and dbatools on our side.

Click through for the command, as well as Jess’s explanation of how it works.

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TLS 1.2 Support in MDAC and SQLOLEDB

Published 2021-03-01 by Kevin Feasel

Ron the Polymath notes a change slipped into Windows:

The October 2020 Preview releases of Windows builds 1809 (KB4580390), 1903/1909 (KB4580386), and 2004/20H2 (KB4580364) include the following change:

– Adds support for the Transport Layer Security (TLS) 1.1 and 1.2 protocols when connecting to SQL Server using the data providers in Microsoft Data Access Components (MDAC).

Click through for Ron’s experience and another update of potential interest.

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Moving SQL Server Data File Locations on Linux

Published 2021-02-26 by Kevin Feasel

Nisarg Upadhyay wants to move files around in SQL Server on Linux:

In this article, I am going to explain how we can move the SQL database files to another location in Ubuntu 18.04. For the demonstration, I have installed Ubuntu 18.04, SQL Server 2019 on Linux on my workstation. You can read SQL Server 2019 on Linux with Ubuntu to understand the step-by-step installation process of the SQL Server 2019 on Linux. We will move database files of AdventureWorks2019 and Wideworldimportors database.

Click through for the process. It’s really similar to Windows in this respect. And, well, in most respects.

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Number of Rows Automatically Sampled versus Table Size

Published 2021-02-26 by Kevin Feasel

Matthew McGiffen does the math:

I mentioned in my previous post about manually updating statistics that you can specify whether they’re updated using a full scan, or you can specify an amount of data to sample, either a percentage of the table size, or a fixed number of rows. You can also choose not to specify this, and SQL Server will decide for you whether to do a full scan, or to sample a certain amount of data.

I thought it would be interesting to look at what the sample sizes are that SQL will choose to use, depending on the amount of data in your table. 

Click through for the result of Matthew’s analysis.

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A Warning on Using Distributed Network Names

Published 2021-02-24 by Kevin Feasel

Allan Hirt has a warning for us:

DNNs are supported as of SQL Server 2019 CU2 and require Windows Server 2016 or later. I wrote more about them in my blog post Configure a WSFC in Azure with Windows Server 2019 for AGs and FCIs. Go there if you want to see what they look like and learn more.

Right now, I cannot wholeheartedly recommend the use of DNNs for listeners or FCIs if you are using Enterprise Edition. Why?

Read on to learn why.

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Memory Grant Feedback in SQL Server

Published 2021-02-24 by Kevin Feasel

Deepthi Goguri hits on one part of Intelligent Query Processing in SQL Server:

In this part, let us focus on the Memory Grant Feedback feature released in SQL Server 2017 for Batch mode execution and in SQL Server 2019 for Row mode execution.

Memory Grants are used by the SQL Server for the Hashes and Sort operations. SQL Server optimizer uses the statistics information and allocate the memory needed by the query before the query executes. When the query is executed, SQL Server uses the allocated memory to process the query for the hashes and sorts. If this memory grant is not enough to process the query, data will use tempdb spilling to disk. When too much memory is allocated based up on the estimates, we can effect the concurrency as all other queries requires memory grants to process the queries as well. Bad estimates can effect the memory grants allocated to the queries. Too much or too little memory grants is bad.

Read on to see how Memory Grant Feedback helps the optimizer out with queries over time.

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So You’ve Run Out of Memory

Published 2021-02-18 by Kevin Feasel

Randolph West explains how the buffer pool handles low-memory situations:

One of the bigger clichés in the data professional vocabulary (behind “it depends”) is that you always give SQL Server as much RAM as you can afford, because it’s going to use it. But what happens when SQL Server runs out of memory?

Recently a question appeared on my post about how the buffer pool works, asking the following (paraphrased):

What happens if a data page doesn’t exist in the buffer pool, and the buffer pool doesn’t have enough free space? Does the buffer pool use TempDB, [and] does TempDB put its dirty pages into the buffer pool?

This is an excellent question (thank you for asking!). I spent 30 minutes writing my reply and then figured it would make a good blog post this week if I fleshed it out a little.

Read the whole thing.

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