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Category: Administration

Graphing CPU Utilization

Published 2016-03-24 by Kevin Feasel

Slava Murygin uses spatial data types to graph CPU utilization on a SQL Server instance:

That diagram provides you about 260 last minutes of Server CPU usage and measured in percents.

As you can see my SQL Server is mostly doing nothing and only during that blog-post writing in the last half and hour or so it is heavily running test scripts to over-utilize my CPU, but it still barely goes more than 60% of CPU (Blue line).

The Red line represents all other processes besides of SQL Server and you can tell if anything else from outside is impacting your performance.

Combined with Glenn Berry’s diagnostic queries, you could generate some quick analytics.  I’d still use R for anything more than slightly complicated, but this is great for those environments in which you don’t have good alternative tooling.

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Reorganize Columnstore Indexes

Published 2016-03-22 by Kevin Feasel

I have a new script available to reorganize columnstore indexes:

Note that this script requires SQL Server 2016 (or later) because the database engine team made some great changes to columnstore indexes, allowing us to use REORGANIZE to clear out deleted rows and compact row groups together, as well as its previous job of marking open delta stores as available for compression.

The code is available as a Gist for now, at least until I decide what to do with it.  Comments are welcome, especially if I’m missing a major reorganize condition.

As mentioned, comments are welcome.

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Index Cannot Be Reorganized

Published 2016-03-21 by Kevin Feasel

Jason Brimhall digs into an error where page-level locking is disabled:

You receive the error message similar to the following:

Msg 2552, Level 16, State 1, Line 1 The index “blah” (partition 1) on table “blah_blah_blah” cannot be reorganized because page level locking is disabled

Immediately, you start double-checking yourself and verifying that it worked the previous night. You even go so far as to confirm that the same index was previously reorganized. How is it possible that it is failing now on this index. What has changed? Has something changed?

There’s an interesting troubleshooting story, but the important message is about setting up a good set of Extended Events so that you can troubleshoot these types of problems.

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Querying Active Directory From SQL Server

Published 2016-03-17 by Kevin Feasel

Ryan Adams shows us how to use OPENROWSET and OPENQUERY to connect to a domain controller and query Active Directory using LDAP:

In the code below, the first thing we do is enable Ad Hoc Distributed Queries so we can try out the OPENROWSET method.  The advantage to this method is not having a linked server and being able to call it directly out of TSQL.  Once we have that enabled we write our query and you’ll notice that we are essentially doing 2 queries.  The first query is the LDAP query inside the OPENROWSET function.  Once those results are returned we are using another query to get what we want from the result set.  Here is where I want you to stop and think about things.  If my LDAP query pulls back 50 attributes, or “columns” in SQL terms, and I tell it I only want 10 of them, what did I just do?  I brought back a ton of extra data over the wire for no reason because I’m not planning to use it.  What we should see here is that the columns on both SELECT statements are the same.  They do not, however, have to be in the same order.  The reason for that is because LDAP does not guarantee to return results in the same order every time.  The attribute or “column” order in your first SELECT statement determines the order of your final result set.  This gives you the opportunity to alias anything if you need to.

You can query LDAP using SELECT statements, but the syntax isn’t T-SQL, so in my case, it was a bit frustrating getting the data I wanted out of Active Directory because I was used to T-SQL niceties.  Nevertheless, this is a good way of pulling down AD data.

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Get Diretory Information For SSAS

Published 2016-03-16 by Kevin Feasel

Jens Vestergaard shows us how to get the Data, Log, Temp, and Backup directories for Analysis Services using Powershell:

Just recently a reply was made to the Connect item, highlighting the fact, that the current values of the Data/Log/Temp and Backup Directories – meaning the currently configured values – is exposed through the Server.ServerProperties collection. According to the answer, only public property values are exposed.

Using PowerShell, we can now retrieve the desired information from any given instance of Analysis Services. Doing so would look something like this:

It’s good to know that this information is available via Powershell.

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Using The Default Trace

Published 2016-03-16 by Kevin Feasel

Jon Morisi shows how to use the default trace:

Often times while troubleshooting an issue, you’ll want more details than what you can find in the application log or SQL Log.  In the background, SQL Server runs a default trace which includes a lot of items to help with troubleshooting including (but not limited to) errors, warnings, and audit data.  I often run the following script as a quick way to find additional details for “ERROR” items from the default trace.

Jon notes that the default trace has been put on the deprecation list, so keep that in mind if you do use it.

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Pulling Non-Clustered Index Data

Published 2016-03-15 by Kevin Feasel

Kenneth Fisher shows using a non-clustered index potentially to reconstruct corrupted data on a clustered index:

So why would you want to do this? Well lets say for example you have a table in a database where the clustered index has become corrupted. Let’s further say that no one mentioned this to you for .. say a year. (No judging!) So your only option at this point might be to use the REPAIR_ALLOW_DATA_LOSS of DBCC CHECKDB. But when you are done how much data has actually been lost? Can you get any of it back?

If you’ve lived a good life and are very lucky, you might recover all data this way.  Otherwise, it’s a good idea to run CHECKDB more frequently and check those backups regularly as well.

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Identify Page Split Sources

Published 2016-03-15 by Kevin Feasel

Dennes Torres shows us how to figure out where bad page splits are occurring:

When one page becomes full and a new page is needed this is reported as a page split, but this is a regular operation with no bad consequences for our queries. The problem happens with updates and non-sequential inserts, when the row needs to be inserted in the middle of the pages of the object and there is no space for this. SQL Server creates a new page, transfers half of the page data to the new page and writes the row data. This creates page fragmentation and is very bad for performance and is also reported as page split.

We can find the bad page splits using the event sql_server.transaction_log. This event monitors all the activities in the transaction log, because that we need to use with caution. We can filter the ‘operation’ field looking for the value 11, which means LOP_DELETE_SPLIT. This is the deletion of rows that happens when SQL Server is moving rows from one page to another in a page split, a bad page split.

It’d be nice to be able to find the particular query causing the page split, and it’d also be nice to find a less resource-intensive method of displaying this information.

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Sys.Messages Error

Published 2016-03-14 by Kevin Feasel

Anup Warrier had an issue recently with sys.messages queries generating an error:

What you normally expect when you run SELECT * FROM sys.messages? The query will return a row for eachmessage_id or language_id of the error messages in the system, for both system-defined and user-defined messages.

Rather than returning the rows, system generated an error for me:

Msg 18058, Level 17, State 0, Line 1
Failed to load format string for error 362, language id 1033. Operating system error: 317(The system cannot find message text for message number 0x%1 in the message file for %2.). Check that the resource file matches SQL Server executable, and resource file in localized directory matches the file under English directory. Also check memory usage.

Anup follows up with the answer, so if you’re running into this issue, check out his post.

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