Category: Administration

Not All Defaults Are Good

Published 2017-06-19 by Kevin Feasel

Nate Johnson rails against bad defaults in SQL Server:

Your servers have many-core CPUs, right? And you want SQL to utilize those cores to the best of its ability, distributing the many users’ workloads fairly amongst them, yes? Damn right, you paid $3k or more per core in freaking licensing costs! “OK”, says SQL Server, “I’ll use all available CPUs for any query with a ‘cost’ over ‘5’“. (To give context here, in case you’re not aware, ‘5’ is a LOW number; most OLTP workload queries are in the double to triple digits). “But wait!”, you protest, “I have more than 1 user, obviously, and I don’t want their horrible queries bringing all CPUs to their knees and forcing the 50 other user queries to wait their turn!”

Nate has a few recommendations here, as well as a picture of kittens.

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Environmental Factors And SQL Server

Published 2017-06-19 by Kevin Feasel

Jeff Mlakar has a set of tips and tricks around SQL Server performance:

Performance problems for a SQL Server based application are likely to be caused by environmental factors and not buggy code.

Whether it is a configuration you can change in SQL Server, Windows Server, VMware, or the network it is likely the first course of action is to perform a quick assessment of the environment. This is where understanding the various configurations and best practices are key. Knowing what to look for can save tons of time.

A mistake I often see is a performance issue is passed off to someone else (more senior) and that engineer assumes a lot of things without checking. People are going to relay the problem as they see it – not as it actually is. This leads to skipping over some elementary checks which can save time and frustration from tracking down imaginary bugs.

Start troubleshooting with a quick environmental check.

There are quite a few checks here.

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Checking Backup Encryption Size Differences

Published 2017-06-15 by Kevin Feasel

Tracy Boggiano has a script to check whether your backup file sizes are larger or smaller when they’re encrypted:

I had a recent project to enable backup encryption on all our servers. Then question from the storage team came up will this required additional space. Well by then I had already enabled in all our test servers so I wrote a query that would compare the average size of backups before encryption to after encryption. Keep in mind we do keep only two weeks of history in our backup tables so this is a fair comparison. If you don’t have maintenance tasks to clean up your backup history then you should have backup_start_time to the where clauses to get more accurate numbers and setup a maintenance tasks to keep your msdb backup history in check.

Unfortunately, Tracy leaves us in suspense regarding whether they did increase.

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Cross-Platform Powershell Remoting

Published 2017-06-14 by Kevin Feasel

Anthony Nocentino shows how to enter Powershell sessions using OpenSSH-basted remoting:

Nothing special here, simple syntax, but the seasoned PowerShell remoting pro will notice that we’re using a new parameter here -HostName. Normally on Windows PowerShell you have the -ComputerName parameter. Now, I don’t know exactly why this is different, but perhaps the PowerShell team needed a way to differentiate between OpenSSH and WinRM based remoting. Further, Enter-PSSession now has a new parameter -SSHTransport which at the moment doesn’t seem to do much since remoting cmdlets currently use OpenSSH by default. But if you read the code comments here, it looks like WinRM will be the default and we can use this switch parameter to specify SSH as the transport.

Once we execute this command, you’ll have a command prompt to the system that passed as a parameter to -HostName. The prompt below indicates you’re on a remote system by putting the server name you’re connected to in square brackets then your normal PowerShell prompt. That’s it, you now have a remote shell. Time to get some work done on that server, eh? Want to get out of the session, just type exit.

It’s interesting to see how well Microsoft is integrating Linux support into Powershell (and vice versa, but that’s a different post).

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Installing Linux And Then SQL Server On Linux

Published 2017-06-12 by Kevin Feasel

David Alcock has a couple posts covering installation of SQL Server on a brand new Ubuntu VM. First, David installs Ubuntu:

The system requirements for running SQL Server on Ubuntu 16.04.2 contains the following

Note

You need at least 3.25GB of memory to run SQL Server on Linux. For other system requirements, see System requirements for SQL Server on Linux.

On the create VM window the Memory is currently set to 1024 MB so by clicking the Customize Hardware button I can change the allocated memory to 4GB (4096 MB) as in the screenshot below:

Then, he explains the process of installing SQL Server:

Let’s break it down a little bit. First sudo, which is giving root permissions to a particular command this is as opposed to sudo su which I had to do later on in the install to switch to superuser mode for the session.

Next is apt. Apt is a command line tool which works with the Advanced Packaging Tool and enables to perform installs, updates and removals of software packages. In this case we’re installing curl so we use the install command.

I think Microsoft did a good job of simplifying the installation process on Linux and making it “Linux-y,” with an easy installation and then post-installation configuration.

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Rebuilding Full-Text Catalogs

Published 2017-06-12 by Kevin Feasel

Thomas Rushton ran into an issue with full-text indexing component versions:

Restoring 27 databases; they all restored properly, but 15 of them gave a warning along these lines:

Warning: Wordbreaker, filter, or protocol handler used by catalog ‘FOOBARBAZ’ does not exist on this instance. Use sp_help_fulltext_catalog_components and sp_help_fulltext_system_components check for mismatching components. Rebuild catalog is recommended.

Read on for the solution.

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Permissions On XML Schema Collections

Published 2017-06-09 by Kevin Feasel

Shane O’Neill diagnoses a permissions issue with XML Schema Collections…or is it?

In my head I’m thinking of all the things that I can do to try and troubleshoot this problem.

Extended Events my session,

Ask my Senior DBA,

Cry

Then I realize that I’m jumping the gun again and I slow down, and check the first error message again. This time without the developers shouting in my ear, about permissions.

This is a great example of why it’s important to troubleshoot using a methodical, logical process. If you get it stuck in your head that the answer is quite obviously something, you lose a bunch of time if it turns out that it isn’t quite as obvious.

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Incorrect PFS Free Space

Published 2017-06-09 by Kevin Feasel

Dave Mason walks through troubleshooting one database corruption scenario:

I’ve been lucky with database corruption during my career. I could probably count on one hand the number of times I’ve had to deal with it. A couple times, it was in a customer’s environment–they managed it themselves, but called me in to help. The other incidents were ones I inherited from a backup I had to restore into a production environment. The first time it happened to me, I didn’t realize it until days later when DBCC CHECKDB ran during a weekend maintenance window. After that, I added a new “rule” to my list: always run DBCC CHECKDB after restoring a database from someone else. That rule paid dividends today.

Here’s the output I saw:
Msg 8914, Level 16, State 1, Line 50
Incorrect PFS free space information for page (1:2564368) in object ID 457768688, index ID 1, partition ID 72057619124060160, alloc unit ID 72057594116767744 (type LOB data). Expected value   0_PCT_FULL, actual value 100_PCT_FULL.
CHECKDB found 0 allocation errors and 1 consistency errors in table 'tbl_Redacted' (object ID 457768688).
CHECKDB found 0 allocation errors and 1 consistency errors in database 'db_redacted'.
repair_allow_data_loss is the minimum repair level for the errors found by DBCC CHECKDB (db_redacted).

Read on to see how Dave solved this issue.

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Synchronizing Logins And Jobs

Published 2017-06-09 by Kevin Feasel

Ryan Adams enumerates several methods for synchronizing logins and SQL Agent jobs across mirrored instances or Availabilty Group replicas:

There is an awesome set of PowerShell cmdlets out there written by MVP Chrissy LeMaire. This method is my personal choice. It works great and is easy to automate. You can run it with SQLAgent or you can just use Scheduled Tasks in the OS. The scheduled tasks method is a little cleaner, but you don’t get to see it in SQL Server. Also if you are on a cluster and running Windows 2012 you can cluster the task scheduler as an added benefit.

Chrissy wrote this with the intent of making migrations easier, and she succeeded. In fact, I made it a point to thank her at MVP Summit last year because it made my life insanely easier. The advantage here is that you can automate a lot more than than just logins. In fact you can migrate and automate pretty much anything at the server level. Here is the link that I guarantee you are going to bookmark followed by a video demo where I show how to install and automate the syncing of logins using both the SQLAgent method and the Scheduled Tasks method.

https://dbatools.io/

DBATools would be my preference in this situation as well, but click through to see four other methods, as well as code.

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Tuning Apache Solr

Published 2017-06-08 by Kevin Feasel

Michael Sun explains how to optimize Apache Solr’s memory usage:

For Oracle JDK 8, both CMS and G1 GC are supported. As rule of thumb, if the heap size is less than 28G, CMS works well. Otherwise G1 is a better choice. If you choose G1, there are more details about G1 configuration in the part 2 of this blog. You can also find helpful guidance in Oracle’s G1 tuning guide.

Meanwhile it’s always a good idea to enable GC logging. The overhead of GC logging is trivial but it gives us a better understanding how the JVM uses memory under the hood. This information is essential in GC troubleshooting. Here is an example of GC logging settings.

There’s some good administrative assistance, but also tips on more efficient querying.

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