Press "Enter" to skip to content

Category: Administration

Compess An Entire Database

Published 2016-01-11 by Kevin Feasel

Shaun J. Stuart has a script which compresses all (compression-worthy) objects in a database:

Reader Dick H. posted a comment on my last version of this script stating that he got an error when this was run against tables containing sparse columns. Data compression does not support tables with sparse columns, so they should be excluded from this process. I’ve modified this script to correct this. I don’t have any tables with sparse columns in my environment, so thanks to Dick for pointing this out!

For instructions on using this script, look here.

This is a very useful script to have in your back pocket.

Comments closed

Row-Level Security

Published 2016-01-11 by Kevin Feasel

Manoj Pandey investigates row-level security:

Here in this post I will talk about the new Block Predicate option available in the CTP 3.0 release. With this option we can restrict write access for specific users.

Block Predicates block all write operations like:

– AFTER INSERT and AFTER UPDATE

– BEFORE UPDATE

– and BEFORE DELETE

I want this to perform well in a busy production environment.  I really, really do.

Comments closed

SQL Server Wants Your RAM

Published 2016-01-11 by Kevin Feasel

Andy Galbraith explains that SQL Server loves RAM:

A frequent complaint we receive comes from a client that has an in-house sysadmin monitoring tool like Microsoft SCOM/SCCM.  They turn the tool on and it startsred-alerting because the Windows server hosting SQL Server is at 90%+ used RAM.  The sysadmin (or local DBA) logs on to the server and finds that there is 5GB free (~4%), and the sqlservr.exe process is using 120GB of the 128GB on the server!

In my experience, VMware administrators tend to be most hung up about this concept.

Comments closed

Setting Up TempDB

Published 2016-01-08 by Kevin Feasel

Chris Shaw tells us to optimize TempDB:

By default when you install SQL Server the TempDB database is not optimized.  For SQL Servers that use the TempDB even moderately, I recommend optimizing it for the best performance.  The TempDB is the storage area that SQL Server uses to store data for a short periods of time, information that can be found in the TempDB include temporary tables, and data that is being sorted for query results. The data in the TempDB is so temporary that each time the SQL Server service restarts, the TempDB is recreated.

Good advice within.

Comments closed

Check Your CHECKDBs

Published 2016-01-07 by Kevin Feasel

Richie Lee has a script to check the last known CHECKDB run date:

One of the most important duties of a DBA is to ensure that CHECKDB is run frequently to ensure that the database is both logically and physically correct. So when inheriting an instance of SQL, it’s usually a good idea to check when the last CHECKDB was last run. And ironically enough, it is actually quite difficult to get this information quickly, especially if you have a lot of databases that you need to check. The obvious way is to run DBCC DBINFO against the specific database. This returns more than just the last time CHECKDB was run, and it is not especially clear which row returned tells us the last CHECKDB (FYI the Field is “dbi_dbccLastKnownGood”.)

It’s a bit of a shame that this information isn’t made available in an easily-queryable DMV.

Comments closed

VLFs

Published 2016-01-06 by Kevin Feasel

Tom Roush talks VLFs, changes in DBCC LOGINFO, and Availability Groups:

Turns out SQL 2008R2 (where the original script worked) returns different fields than 2012 and 2014 (where it didn’t).

I figured I didn’t want to find out which version of the script to use every time I needed to run it on a server, so I told the script to figure that out by itself, and then run the appropriate hunk of code (example below)

This is a good explanation of how to back out of a complex situation.

Comments closed

Change Azure SQL Database Compatibility Level

Published 2016-01-06 by Kevin Feasel

Tom LaRock shows us how to change the compatibility level of an Azure SQL Database:

You can change the compatibility level of an Azure SQL Database.

It’s true! I know!

OK, so I’m a little excited about this one. See, I’ve been giving this talk on cardinality for the past couple of years now, so this is a hidden gem to me. When I found out this was possible I took out my demo scripts to see if changing the compatibility level would have any effect.

This is interesting, especially given that Management Studio doesn’t give you that option.  Know your T-SQL, folks.

Comments closed

Trickle Migration

Published 2016-01-05 by Kevin Feasel

Richie Lee encountered a use case for trickle migration:

Recently I needed to apply compression data on a particularly large table. One of the main reasons for applying compression was because the database was extremely low on space, in both the data and the log files. To make matters worse, the data and log files were nowhere near big enough to accommodate compressing the entire table in one go. If the able was partitioned then I could have done one partition at a time and all my problems would go away. No such luck.

Best way to eat an elephant, etc. etc.  Read the whole thing; you might be in a similar situation someday.

Comments closed

Trace Flags Without Sysadmin

Published 2016-01-01 by Kevin Feasel

Jack Li shows how to enable a trace flag without sysadmin or changing any application code:

The initial thought is to enable the trace flag at session level.  We ran into two challenges.  First, application needs code change (which they couldn’t do) to enable it.  Secondly, dbcc traceon requires sysadmin rights.   Customer’s application used a non-sysadmin user.  These two restrictions made it seem impossible to use the trace flag.

However, we eventually came up with a way of using logon trigger coupled with wrapping the dbcc traceon command inside a stored procedure.   In doing so, we solved all problems.  We were able to isolate the trace flag just to that application without requiring sysadmin login.

This is the very edge of an edge case.  In normal practice, change the code.

Comments closed

Trustworthy Databases

Published 2016-01-01 by Kevin Feasel

Kenneth Fisher asks if you check TRUSTWORTHY settings on your databases:

I wasn’t surprised (although a little disappointed) that out of the 9 people the answered only one person was, and of the rest 5 didn’t even know what TRUSTWORTHY is. I even had one person ask me later. That’s somewhat scary because under the right circumstances if you give me a database with TRUSTWORTHY turned on I can take over your instance. I’m NOT going to show you how but it isn’t terribly difficult.

I’ll admit that I have been a bit non-chalant about TRUSTWORTHY in the past, but turning it on is the smart move.

Comments closed