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Day: February 11, 2016

Exfiltrating Data In TDE-Protected Databases

Published 2016-02-11 by Kevin Feasel

Tom LaRock shows how to exfiltrate data in a database protected by Transparent Data Encryption:

Enabling TDE does not protect your BACPAC files, just your database backups. If you are relying on TDE to protect your data at rest then allowing users to create BACPAC files will put you at risk. But no more risk than any other user choosing to run a SELECT statement and save the data somewhere (or perhapsjust use PowerBI to open a connection and import to Excel).

TDE has a single, specific purpose.  If you want something more stringent, SQL Server 2016 Always Encrypted might be an option.

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Simple Recovery Mode And Transaction Logs

Published 2016-02-11 by Kevin Feasel

Kenneth Fisher discusses changing your database’s recovery model to Simple in order to clean out a transaction log:

Clearing out a full transaction log is a common problem. A quick search will find you dozens of forum entries and blog posts. Because of that I’m not going to talk about the correct methods of dealing with a transaction log full error. What I want to discuss is why you shouldn’t use the following method.

And Kenneth also hits the one legitimate use:  dire emergency.  If this is a normal part of some process (e.g., warehouse loading), bite the bullet and either live in Simple recovery mode (understanding the risks) or get the disk space to keep it in Full mode.  Switching back and forth—especially if you aren’t taking full backups immediately after switching back—is a good way to get yourself burned.

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Custom SSAS Assemblies

Published 2016-02-11 by Kevin Feasel

Jens Vestergaard shows us custom assemblies in SSAS:

The example in this post will be the well known Hello World example in the context of SSAS, and I trust this will illustrate the possibilities with this technique well enough, for you to apply your own solution, to your challenges.

If you’re at all familiar with CLR in the database engine, this looks to be the Analysis Services equivalent.  Hopefully it doesn’t have the same “We can’t possibly use this!” taboo that CLR seems to have in the database engine world.

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Backup Problems

Published 2016-02-11 by Kevin Feasel

Kendra Little has a few warning signs for backups:

5. Your log backups run every 30 minutes. I have yet to find a company with log backups running every 30 minutes who was actually OK with losing 30+ minutes of data. Maybe you are part of the company where it’s actually true, but if you’re not 100% sure, get someone to sign off on it. With an ink pen. Really.

Funnily enough, I’ve experienced exactly this, except the business side was flabbergasted that I wanted to take transaction log backups so quickly—they had a 24-hour RPO, so why bother with such frequent backups?  I kept a straight face and explained that if I had my druthers, I’d take a transaction log backup every 1-3 minutes.

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CROSS APPLY

Published 2016-02-11 by Kevin Feasel

Steve Jones compares writing a function versus using CROSS APPLY to write the same function:

The conclusion I’d take here is that CROSS APPLY ought to be a tool you keep in the front of your toolbox and use when you must execute a function for each row of a set of tables. This is one of the T-SQL  techniques that I never learned early in my career (it wasn’t available), and I haven’t used much outside of looking for execution plans, but it’s a join capability I will certainly look to use in the future.

I’m one of the biggest fans of the APPLY operator out there—my favorite talk is based on it, even.  But in this case, I’m going to say that writing “CROSS APPLY” really didn’t do anything here—times are similar enough that I’d be suspicious that the database engine is doing the same thing both times.

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