Press "Enter" to skip to content

Category: Administration

Troubleshooting Out-of-Memory Errors in SQL Server’s Database Engine

Published 2022-03-31 by Kevin Feasel

Dimitri Furman shows off a DMV:

As part of our efforts to improve database engine supportability, we have added a new dynamic management view (DMV), sys.dm_os_out_of_memory_events. It is now available in Azure SQL Database and Azure SQL Managed Instance and will become available in a future version of SQL Server. If an out-of-memory (OOM) event occurs in the database engine, this view will provide details to help you troubleshoot the problem, including the OOM cause, memory consumption by the database engine components at the time of event, potential memory leaks (if any), and other relevant information.

Read on to learn more about it, as well as a corresponding Extended Event.

Comments closed

Finding Free Space in a SQL Server Filegroup

Published 2022-03-29 by Kevin Feasel

John McCormack does some digging:

I just realised that in all my scripts that I use on a regular basis, I didn’t have one for working out free space in SQL Server filegroups. It’s not something that comes up too often but it’s handy to know. For methods of working out space in individual files, you could refer to this post on mssqltips.

Click through for the query and congrats to John on 100 posts.

Comments closed

The Practical Costs of Index Fragmentation

Published 2022-03-29 by Kevin Feasel

Tibor Karaszi digs into index performance:

See numbers and diagrams at the end, or at the top. I measured a few cases: the difference between no external fragmentation and severe external fragmentation (over 99%). I have both a narrow index and a wide index, and I read one (1), 10,000 and 100,000 rows using index searches (“range scan”). There were obviously no difference reading 1 row so I exclude that from my discussion below. For the other cases the extra time with an extreme level of external fragmentation is (from lowest impact to highest) 7%, 10%, 13% and 32%. The highest number (32%) is when reading many rows from a narrow index, i.e. many rows per page. Again, this is with an extreme level of fragmentation.

What’s interesting is that for the most part, there’s a negligible difference between ~0% internal fragmentation and ~99% internal fragmentation. The follow-on question is, how much are defrag operations costing you in performance and when is the benefit worth the cost?

Comments closed

Determining if SQL Server Needs More Memory

Published 2022-03-29 by Kevin Feasel

Erik Darling breaks Betteridge’s Law of Headlines:

In this post, we’ll talk about how to figure out if your SQL Server needs more memory, and if there’s anything you can do to make better use of memory at the same time.

After all, you could be doing just fine.

(You’re probably not.)

I have a simple flow chart: do you have all of the memory created since the 1990s? If not, then you need more memory. If so, may I please borrow a cup of RAM?

Comments closed

Failure to Write to the Security Event Log

Published 2022-03-24 by Kevin Feasel

Sean Gallardy files events to the circular file:

Getting back on track instead of listening to me complain, many DBA’s and internal security folks like writing to the Windows Security Event Log because the word security is in the name and they have some tool like Splunk that automatically collects these details. I like automation, so that’s a nice win. However, you may be running into SQL Server error 33204 which is a failure to write an audit event to the security event log.

Read on to find one reason why this might happen.

Comments closed

So You Want to Migrate a SQL Server

Published 2022-03-24 by Kevin Feasel

Jon Biggs has a guide for us:

We are currently performing migrations with upgrade of multiple-instance SQL Servers to new servers. The migrations are going smoothly (knock on wood), and I wanted to relay some information about the migration process. There are four phases you need to perform when migrating a SQL instance to a new server. These phases are Review, Prepare, Test, and Migrate. It sounds simple enough but let’s take a deeper look into what goes into each phase.

Read on for Jon’s take on the migration process.

Comments closed

Finding SQL Agent Jobs with Invalid Job Owners

Published 2022-03-22 by Kevin Feasel

Chad Callihan is trying to clean up this town:

Do you know which account is the owner for your SQL Server Agent jobs? Some jobs might be owned by user accounts which can become a problem. What happens if that job owner isn’t around forever and goes away? Will that job just keep chugging along?

Without an existing owner, a SQL Server Agent job will not run. Once a user gets disabled or removed from Active Directory, a job is still going to try running under that user but will begin failing.

Click through to see what kind of errors you might find.

Comments closed

Managed Instance Link in Preview

Published 2022-03-18 by Kevin Feasel

Dani Ljepava announces support for Managed Instance link is now in public preview:

As of today, we are pleased to announce that the link feature for Managed Instance is available in the open public preview, in all Azure regions worldwide. It can be used with existing, or new managed instances, and SQL Server 2019 Enterprise, or Developer edition, including SQL Server 2022 CTP (available through EAP). We have also released the tooling support for the link in the form of automated wizards available in SQL Server Management Studio, starting from SSMS v18.11.1.

With the link, replicated databases from SQL Server on Managed Instance are usable as R/O secondary replicas. While the link is in operation, transactions commited on SQL Server (primary) are instantaneously committed to Managed Instance (secondary). This provides an exact replica of your SQL Server database on Managed Instance, synced near real-time. The link was built to be resilient, in case of the network being down, SQL Server being rebooted, or maintained, or in case of some other issue, the link will automatically resume replicating where it has left off when the issue has been resolved.

Support for 2019 is a shrewd idea, given the SQL Server version adoption curve for companies. This isn’t going to replace having a proper availability group for high availability or even (most) disaster recovery options, though, because the link is currently one-way—though Dani does mention eventual support for bi-directional operation with SQL Server 2022.

Comments closed

Creating a Trust between On-Prem AD and AWS Directory Service

Published 2022-03-16 by Kevin Feasel

Tom Collins makes a connection:

Most SQL Servers use a large portion of the authentication as Windows Authentication – utilising Kerberos and NTLM protocols via Active Directory. So when it comes to considering moving on-prem SQL Server resources to Cloud Providers – Active Directory is a foundational question.    There are other methods than Microsoft Directory – which I’ll discuss in future posts.

Utilising AWS RDS SQL Server with Windows Authentication methods is only possible using the AWS Directory Service.  i.e The AWS RDS SQL Server is created and added as a resource to the AWS Directory Service . If on-prem users require access to the AWS RDS SQL Server via Kerberos , a forest trust is required between the AWS Directory Service and the on-prem AD. 

For this post – the focus is on an existing on-premises SQL Server inventory using Microsoft Active Directory Services.

Read on to see what you’d need to do to implement this.

Comments closed