Compressed Backup Errors

Kenneth Fisher explains why you might get “out of space” errors when taking compressed backups:

Compressing your backups has very few downsides. It’s usually faster (the additional time for compression is less than the time saved by reduced IO) and of course, the backups are smaller. I have run into a few issues, however.

On one occasion there was 75gb free on a drive, the last full backup was only 50gb and the database had not grown significantly in size. Interestingly there was an error when we tried to run a backup. Not enough disk space.

Read on for the explanation as well as the solution.

Cost Threshold For Parallelism Testing

Tim Peters shows that the Dynamics people are probably right with their assertion regarding Cost Threshold for Parallelism:

These plans are from a SQL Server 2008 R2 SP3 instance that runs a version of Microsoft Dynamics. The MS Dynamics team knows their product issues a bunch of really small queries and recommend a Max Degree of Parallelism of 1. In my case there is one query plan with a cost of 34,402 query bucks that a MAXDOP = 1 can’t afford. Increasing the MAXDOP from 1 while keeping the Cost Threshold at 5 will keep all of my little queries running in their single threaded paradise while allowing some infrequent biguns to spread their lovely wings across a few more threads. My Cost Threshold For Parallelism is set to 5 and I hope to never have to defend my settings in a dark alley with Erik Darling.

Different systems will behave in different ways, so it makes sense that they might require different settings.  In the case of Dynamics, it appears that almost all of the queries are extremely low-cost, so relatively few plans would go parallel and the ones that do, you probably want going parallel.

T-SQL Tuesday 88 Roundup

Kennie Nybo Pontoppidan has a roundup for this week’s T-SQL Tuesday:

Last duty for me as a T-SQL Tuesday host is to write up a summary of all the posts. Soooo, here we go…

Kennie goes the extra mile and summarizes each story with a moral.

TDE And Encrypted Backups

Arun Sirpal shows that Transparent Data Encryption will also lead to encrypted backups:

Ok great let’s check this backup file using a cool tool (XVI32). I really want the contact number of a guy called SQLDOUBLEG because I need his help tuning my SQL Servers so I go looking for a text string, hopefully the phone number will be close by.

As Arun points out, you don’t need TDE to get encrypted backups, but it does the job.

Testing Backups With dbatools

Sander Stad shows how to test database restorations en masse using dbatools:

Testing your backups is a tedious job and it takes a lot of time which I as a DBA don’t have. I don’t have the time to restore a database, run a DBCC command for every database that’s backed up.

There is a solution and it’s called “Test-DbaLastBackup” which is part of the dbatools module.

Rob Sewell also has a recent post on the topic.

Restoring Databases With dbatools

Rob Sewell shows how to restore a slew of databases using one dbatools command:

In my lab I had installed SQL 2016 on a server running Server 2016 TP5 which expired so I needed to re-install Windows and therefore needed to restore all of my user databases again. This was so easy using the dbatools module that I thought it was worth sharing to show how easy your disaster recovery process could be.

Having re-installed Windows and SQL and copied the backup files back to the server (although I could have used a network location), I then had to restore all of the user databases.

This is how I restored all of my user databases using the dbatools module command Restore-SQLBackupFromDirectory

Read on for the answer, as well as a warning that the upcoming dbatools 1.0 release may change some things.

Power BI Matrix Preview

Matt Allington reports that Power BI Desktop supports a new type of matrix (in preview):

Expand, Collapse, Drill and Filter

Expand and collapse behaves just like a pivot table however with a slightly different UI. The new matrix experience is however entirely consistent with the chart drill experience so it is very intuitive.

The new cross filter behaviour is of course not possible in a regular pivot table in Excel (without VBA). You can select any column, row or cell in the matrix and it will cross drill the other visuals on the canvas as can be seen above.

This looks like an interesting change, and Matt shows how to enable the preview.

SSRS: SendGrid Without Encryption

Denny Cherry shows how to configure Reporting Services to use SendGrid (sans encryption) to send e-mails:

We setup our nice new SQL 2016 SSRS servers to authenticate using the new SQL 2016 GUI which just supports it now. One problem with the GUI is that it requires that you use encryption. No big deal, SendGrid supports encrypted SMTP.

The problem with SendGrids encrypted SMTP is that it has a funky certificate chain which isn’t trusted by default. And it’s a convoluted process to get the correct certificate chain installed on a few servers (we have an SSRS farm as there’s thousands of reports being delivered every morning).

Click through for the solution.

Data Type Mismatches

Kendra Little gets into why certain data type mismatches force scans of tables while others can still allow seeks:

Sometimes we get lucky comparing a literal value to a column of a different type.

But this is very complicated, and joining on two columns of different types in the same family without explicitly converting the type of one of the columns resulted in worse performance in Paul White’s tests, when the columns allowed NULLs! (Note: I haven’t rerun those tests on 2016, but I think the general advice below still applies.)

General advice: don’t rely on being lucky. Pay attention to your data types, and compare values of the same data type wherever possible.

That’s great advice.

PBM Schedule Failures

Dave Turpin diagnoses an issue where scheduled Policy-Based Management policy checks were failing:

While it is easy to build and test policies by executing them on demand (especially powerful when run through Central Management Server) I had some issues getting my policies to run in “on schedule” mode.

To be more specific, my policies that use the ExecuteSQL function have been an issue.  What I was finding was:

  • The policy would run fine “on demand” but…
  • When I run the policy through the PBM scheduler, the policy would fail.

Dealing with false positives is not a good start for any monitoring service, so getting to the root of the issue was critical.

Read on for the solution.


March 2017
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