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Day: January 5, 2021

Cross-Validation in Azure ML Studio

Dinesh Asanka takes us through the cross-validation component in Azure ML Studio:

Let us look at implementing Cross-Validation in Azure Machine Learning. Let us use the sample Adventure Works database that we used for all the articles.

Then Cross Validate Model is dragged and dropped to the experiment. The Cross Validate model has two inputs and two outputs. Two inputs are data input and the relation to the Machine Learning technique. Let us use the Two-Class Decision Jungle as the Machine Learning Technique. Then the first output is connected to the Evaluate Model as shown in the following figure:

Click through for the process.

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Adjusting Database Settings with Powershell

Eric Cobb takes a look at some nice functionality in dbatools:

There may be times that you want to ensure certain settings are applied to a database, or multiple databases. For example, if you restore a Production database to a QA environment, you may need to change the Recovery Model. Or if you’re migrating databases to a new SQL Server version you want to make sure to update the Compatibility Level. With dbatools this is really, really easy. Here are some examples:

Read on for examples around setting the database owner, changing the compatibility level, and setting the recovery model.

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Kerberos vs NTLM

Jack Vamvas contrasts Kerberos and NTLM:

There is a message found in SQL Server Error Logs similar to 

The SQL Server Network Interface library could not register the Service Principal Name (SPN) [ MSSQLSvc/ ] for the SQL Server service. Windows return code: 0x200b, state: 15. Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies and if the SPN has not been manually registered.

The line I’m interested in reviewing is Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos.   It’s good to first understand the differences between Kerberos & NTLM – both supported by SQL Server during AD authentication

Read the whole thing. It’s easy to fall into the trap of “Windows authentication = Kerberos”—I do that myself far too often.

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PFS Contention and Heaps

Uwe Ricken continues a series on heaps in SQL Server:

The PFS page “can” become a bottleneck for a heap if many data records are entered in the heap in the shortest possible time. How often the PFS page has to be updated depends mostly on the data record’s size to be saved.

This procedure does not apply to clustered indexes since data records in an index must ALWAYS be “sorted” into the data volume according to the defined index value. Therefore, the search for a “free” space is not carried out via the PFS page but via the value of the key attribute!

Read on for more detail.

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Identifying Expensive Queries with Query Store

Matthew McGiffen has a query for us:

Some time ago I wrote a query store version of the “Top 20 queries” query that will produce a ranked list of your most expensive queries – and I’ve ended up using this a lot.

The only downside of using the DMVs for Query Store is that they are per database whereas dm_exec_query_stats is a view across the whole instance. So I had to use a cursor and a temp table, populating the temp table for each database in turn.

Click through for the query.

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