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Category: Administration

A Look At Automatic Plan Tuning In SQL Server 2017

Published 2018-09-11 by Kevin Feasel

John Sterrett shows us how to review automatic plan tuning suggestions:

SQL Server 2017 Automatic Tuning looks for queries where execution plans change and performance regresses. This feature depends on Query Store being enabled. Note, even if you don’t turn on Automatic Tuning you still get the benefits of having access to the data. That is right. Automatic Tuning would tell you what it would do if it was enabled.  Think of this as free performance tuning training.  Go look at the DMVs and try to understand why the optimizer would want to lock in an execution plan. We will actually go through a real-world example:

Click through for the example.  I wouldn’t automatically trust these automatic results, but my experience has been generally positive.

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Migrating Azure SQL Databases Between Resource Groups

Published 2018-09-07 by Kevin Feasel

Arun Sirpal shows us a method for moving Azure SQL Databases between resource groups:

In my mind there are a couple of ways to move a database across resource groups. They vary from scripting to just using the Azure portal. I am going to use the Azure portal and do the following.

  1. Export a database in resource group X to a storage account Z.
  2. Import the file from the storage account Z into a database that is in resource group Y.

It’s just like a “backup and restore” strategy, all with the assumption that you are working within the same subscription ID.

Read on for a step-by-step demonstration on how to do this.

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Changing Language In SQL Server

Published 2018-09-05 by Kevin Feasel

Jeff Mlakar shows how to switch languages in SQL Server:

The SET LANGUAGE command allows us to choose a language for a session. By session here I mean by SPID. Each query tab you open in SSMS is another thread to the database and receives a SPID. This can be called by almost anyone who has permissions to access the database because it only requires membership in the public role to execute.

Now let us change the session language to Russian.

You can change the default language for all sessions, as well as switching language for a specific session.

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What To Do After Installing SQL Server On Linux

Published 2018-08-31 by Kevin Feasel

Manoj Pandey has a few tips for what to do after installing SQL Server on Linux:

Here are some of the best practices post installing SQL Server on Linux that can help you maximize database performance:

1. To maintain efficient Linux and SQL Scheduling behavior, it’s recommended to use the ALTER SERVER CONFIGURATION command to set PROCESS AFFINITY for all the NUMANODEs and/or CPUs. [Setting Process Affinity]

2. To reduce the risk of tempdb concurrency slowdowns in high performance environments, configure multiple tempdb files by adding additional tempdb files by using the ADD FILE command. [tempdb Contention]

3. Use mssql-conf to configure the memory limit and ensure there’s enough free physical memory for the Linux operating system.

Some of these are common for Windows and Linux (like multiple tempdb files) but there are several Linux-specific items here.

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Catalog Your SQL Servers: The SQL Undercover Catalogue

Published 2018-08-29 by Kevin Feasel

David Fowler announces the SQL Undercover Catalogue:

Where Can I Get the Catalogue From?

The Undercover Catalogue is available from our GitHub site.

What Does the Catalogue Store?

The Undercover Catalogue stores all manner of useful information on your SQL Servers,

  • Instances –
  • Databases
  • Logins
  • Users and permissions
  • Agent Jobs

with many more modules planned in future releases.

Check it out and I’m sure they’d love feedback.  Also, read on for where this toolkit is going.

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Finding Dependencies In SQL Server Objects

Published 2018-08-24 by Kevin Feasel

Lori Brown walks us through the sys.dm_sql_referencing_entities and referenced entities DMVs:

In both cases you can see that sys.sql_expression_dependencies provides the same basic info.  But when it comes to tables are referenced by a stored procedure, sys.sql_expression_dependencies gives you less detail than you can get when using sys.dm_sql_referenced_entities.  The biggest difference in both examples is that with sys.sql_expression_dependencies you will get info on cross-database and cross-server dependencies which can be super helpful.

However, once again I have to sound a note of caution because even sys.sql_expression_dependencies does not catch things referenced in a dynamic SQL string.  Sales.Orders is found in dynamic SQL in the, [Application].[Configuration_EnableInMemory] & [DataLoadSimulation].[Configuration_ApplyDataLoadSimulationProcedures] stored procedures but it does not catch this.  So far the best way to find objects in dynamic SQL strings that I know of is to check for the object in sys.sql_modules.

Read the whole thing.

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Finding A Schema’s Owner

Published 2018-08-24 by Kevin Feasel

Jack Vamvas shows how to find out which user owns a particular schema in a database:

Question: How can I find the owner of a SQL Server schema ?   I want o find the owner through a t-sql solultion , rather than looking through the GUI.

Answer: To find a schema owner you can use either sys.schema view or the information_schema.schemata. Since SQL 2005,  information_schema.schemata has come into line with sys.schema.     information_schema.schemata returns schemas just from the current database.

Click through for simple examples of both methods.

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Storing Wait Stats In tempdb

Published 2018-08-14 by Kevin Feasel

Max Vernon has a script which loads a bunch of wait stats definitions and then collects wait stat details:

Performance troubleshooting should begin with capturing wait stats so we can understand where SQL Server is busy. The script below captures wait stats into a table in tempdb; the script should be ran via a SQL Server Agent job or some other scheduling mechanism.

I like the definitions that Max provides.  My only recommendation would be to store this data someplace a bit more permanent than tempdb.

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Configuring tempdb

Published 2018-08-13 by Kevin Feasel

Jeff Mlakar looks at some basic guidelines for tempdb and shows how to configure this database:

The basic guidelines are:

  • Each tempdb data file should be the same initial size

  • Autogrowth to tempdb files should be an explicit value in MB instead of a percentage. Choose a reasonable value based on the workload. Ex. 64MB, 128MB, 256MB, etc.

  • The number of tempdb files should be 1 per logical processor core up to 8. At that point the performance should be monitored and if more tempdb files are needed they should be added in sets of 4.

  • Ideally the tempdb files are sized up to the max they will need and never have to autogrow.

  • Use trace flags 1117 and 1118 for versions of SQL Server < 2016. In SQL Server 2016 these trace flags are defaults.

    • Trace flag 1117: when a file in the filegroup meets the autogrow threshold, all files in the filegroup grow together

    • Trace flag 1118: Removes most single page allocations on the server, reducing contention on the SGAM page. TLDR; no more mixed extents – use the whole page.

There are some good pieces of advice here, and Jeff includes a great example of a terrible setup.

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So You Locked Out Your Sysadmin User…What Next?

Published 2018-08-08 by Kevin Feasel

Sreekanth Bandarla shows how you can recover from having your sysadmin user account locked out or removed:

In this blog post, let’s see how to regain admin access on a SQL Server Instance in case you lost it by mistake or for whatever reason. It’s not a very common scenario, but hey you never know. I ran into this some time last week(Fortunately it’s in our POC environment), Okay, Here’s the deal – we have a POC SQL Instance which was installed by an individual who is no longer working with us and apparently he forgot to make our DBA grp as sysadmins. Basically we don’t have admin rights to our own SQL Instance, SA account is disabled(Well, No one has no clue what that pwd was to begin with). So, how did we recover from this disastrous event?

This is the “fake rock with a key in it” workaround.  Also, a good reason why there should be as few local administrators on your Windows machines as you can get away with.

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