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Category: Administration

Batch Mode on Rowstore in SQL Server

Published 2020-06-17 by Kevin Feasel

Monica Rathbun introduces us to one of the biggest internal improvements for SQL Server 2019:

Under compatibility level 150, in both SQL Server 2019 and Azure SQL Database, you now can use batch mode for CPU-bound analytic type workloads without requiring columnstore indexes. There is no action needed to turn on batch mode aside from being on the proper compatibility mode. You also have the ability to enable it as a database scoped configuration option (as shown below), and you can hint individual queries to either use or not use batch mode (also shown below). If you recall in my earlier blogs on columnstore, it is batch mode in conjunction with page compression that drastically increases query performance. This feature, Batch Mode on Rowstore, allows all operators enabled for batch mode to operate as such in SQL Server.

What does this mean? It means that query operations can process data faster, more efficiently and mimic what makes columnstore so fast. Instead of reading row by row (row store mode) it can read in chunks i.e. batches of 900 rows at a time. The performance impact of this can be tremendous which effectively uses CPU more efficiently.

Read on to see the limitations and benefits.

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Altering the Database without Rolling Back Users

Published 2020-06-12 by Kevin Feasel

Kenneth Fisher wants to change a database:

If this strikes a bit too close to home for you then you need to look at the ROLLBACK clause. It’s great for killing and rolling back all of the current connections before making my change.

But this is a pretty sensitive app and if there’s something running I have to let it finish. No ROLLBACK allowed. But I’m also not going to wait forever to see if my alter is going to happen. Turns out there is a nice easy option for this too.

Click through to see the option, as well as the message you get if it can’t work immediately.

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Backing Up SQL Server Instance Configuration

Published 2020-06-05 by Kevin Feasel

Claudio Silva has started a series on backing up your SQL Server instance configuration. Part 1 walks us through the basic process:

If you have never used this command, you can test for a single instance by running the following:

Export-DbaInstance -SqlInstance "devInstance" -Path "D:\temp"

This will create all scripts in the D:\temp folder. A folder named “devInstance-{date}” will be created.
In this folder, you will find 1 file per ‘object type’. The file names are in the form of “#-.sql” where the # is a number that represents the iterator on the order that the internal calls of the underlying functions happen.

Be sure to read the sections around passwords!

Part 2 introduces parallelism into the mix:

There are a couple of options, like the native PowerShell cmdlets Start-Job/Stop-Job a.k.a background jobs, Runspaces jobs and Thread jobs but I will just mention two of them. One is a nice addition to the most recent version of PowerShell (v7) and the other using a PowerShell module.

In case you don’t know, with PowerShell v7 it’s possible to use a new option -Parallel with ForEach-Object. Check PowerShell’s team blog post PowerShell ForEach-Object Parallel Feature.

However, because I don’t have (yet :-)) PS7, I will keep leveraging on PoshRSJob module, which uses runspaces, created by Boe Prox (T | B).

There’s a lot of meat in that second part, so check it out.

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Alerting when Power BI Tenant Settings Change

Published 2020-06-04 by Kevin Feasel

Melissa Coates walks us through how to track Power BI tenant settings changes:

This post discusses two methods of receiving an alert when a tenant setting has changed in the Power BI Service: one using Cloud App Security, and the other using the M365 Security & Compliance Center.

Tenant settings in the Power BI Service are among the most important things to get right. Once they are set the way you want, the objective is to ensure all changes are well-controlled. Tip: Check section 10 in the Planning a Power BI Enterprise Deployment whitepaper—I included some tenant setting recommendations in the latest version.

Read on to see how.

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Updated SQL Server Diagnostic Queries

Published 2020-06-03 by Kevin Feasel

Glenn Berry has an updated set of DMV queries for us:

These are my SQL Server Diagnostic Information Queries for June 2020, aka my DMV Diagnostic Queries. They allow you to get a very comprehensive view of the configuration and performance of your SQL Server instance in a short amount of time. There are separate versions of these T-SQL queries for SQL Server 2005 through SQL Server 2019. I also have separate versions for SQL Managed Instance and Azure SQL Database. My diagnostic queries have been used by many people around the world since 2009. I make regular improvements to these queries each month.

This is one of my favorite methods for learning about a new SQL Server instance.

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Migrating from Azure SQL DB to an Azure SQL Managed Instance

Published 2020-06-02 by Kevin Feasel

Eitan Blumin walks us through the process of moving from Azure SQL Database to an Azure SQL Managed Instance:

What we cannot do:

– You cannot backup and restore from Azure SQL DB to a Managed Instance.
– You cannot use Azure SQL DB as a source in Azure Data Migration Service (DMS).
– You cannot use Azure SQL DB as a source in Data Migration Assistant (DMA).
– You cannot use Azure SQL DB as a source in DB Mirroring, AlwaysOn, Transaction Log Shipping, or Replication.
– Implementing a custom T-SQL, SSIS, or ADF (Azure Data Factory) solution will be too complicated, and will require an unacceptable development overhead.

That last one is a bit iffy, though Eitan’s two solutions are going to be easier than a custom solution.

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Surviving an Audit: Backup History

Published 2020-06-01 by Kevin Feasel

Dave Bland talks about surviving an audit:

Don’t volunteer information

Only provide the evidence they are asking for, nothing more.  You want to avoid giving them things that they do not ask for.  By doing so, you might expose something that you don’t want them to see.  The last thing you want to do, is give them a reason for documenting a finding. Another thing to remember is the audits have a defined scope.

This is some of the best advice about audits out there, particularly when combined with the other points Dave makes about being honest and doing the right thing. Dave also ties in some information about backup history as a particular auditing example.

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TDE and Managed Instances

Published 2020-05-28 by Kevin Feasel

Tim Radney notes a change to the way new Azure SQL Database Managed Instance databases are configured:

Another recent change is that all newly created databases have “Encryption Enabled” set to True. This enables Transparent Data Encryption. By default, if you haven’t created your own key, it will use the service-managed key. A bug I’ve found in SSMS is that even though you set “Encryption Enabled” to false, it will still enable TDE. This is not the behavior when using T-SQL.

Read on to understand the ramifications of this change.

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Preventing Unexpected Failover with AG Patching

Published 2020-05-27 by Kevin Feasel

Josh Darnell dealt with an issue with Availability Groups:

I had a 2-node availability group (AG) + fileshare witness system experience an unexpected failover recently.

The synchronous secondary was being patched, and when it came back up from a reboot, the current primary unexpectedly failed over. We weren’t done with all the patching on the secondary, so this caused a short outage, and we had to fail back to the original primary to finish the patching (which is of course another short interruption in availability).

The root cause was interesting enough that I decided to share the story here, and provide some general advice and debugging tips along the way.

Click through to understand why this happened and how you might be able to avoid the pain Josh experienced.

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