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Category: Administration

Troubleshooting High Threadpool Waits and Deadlocked Schedulers

Eitan Blumin takes us through a troubleshooting scenario:

In short, high THREADPOOL waits can happen when SQL Server doesn’t have enough “worker threads” to handle new tasks, which could cause SQL Server to hang and refuse connections. When a task is waiting for a worker thread to become available, that wait type is called THREADPOOL wait.

A background process, called “Scheduler Monitor“, will identify when the same worker threads are “stuck” in the same state for 60 seconds or more. In which case it will resolve the issue as a Deadlocked Scheduler, and that’ll cause dropped connections, rollbacks, and even fail-overs.

When a Deadlocked Scheduler event happens, SQL Server will automatically generate a memory dump file (SQLDump#####.mdmp), and log the incident in the SQL Server Error Log.

Read on to understand what causes this as well as why we always fumble our keys under the car as the scary monster approaches.

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Azure Arc Deployment Options for SQL Server

Sasha Nosov takes us through Azure Arc deployment options for SQL Server:

As you can see, both on-Azure and off-Azure options offer you a choice between IaaS and PaaS. The IaaS category targets the applications that cannot be changed because of the SQL version dependency, ISV certification or simply because the lack of in-house expertise to modernize. The PaaS category targets the applications that will benefit from modernization by leveraging the latest SQL features, gaining a better SLA and reducing the management complexity.

Click through for a graphic, as well as further clarification on each item.

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Find and Modify File Growth Settings Across Databases

Lori Brown has a challenge:

To some of you out there, that many databases might not be a big deal.  To me, it is a big deal.  That many databases can cause many admin tasks to take a very long time.  One such task is to review all databases to make sure that they are not growing their files by 1MB or 10 Percent, especially the transaction log files.  I find those default settings to not be a good thing generally, and have learned to set files to grow by specified amounts if auto growth needs to occur.  I also try to manually grow data files during maintenance periods but we all know that auto growth happens.

So…how do we find out if our databases have 1MB or 10 Percent file growth set up?

Click through for a script which finds default-sized databases, as well as a script to fix them.

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Finding Unused SQL Server Tables

Nisarg Upadhyay shares a few techniques to look for whether a table is currently in use:

In this article, I am going to demonstrate how we can identify the unused tables of a given SQL Database. As a database administrator, we must maintain the tables and objects of the SQL Database. In my organization, when we add a new column or change the data type of a column, we export the data of the existing table in the backup table. Often, we forgot to review and maintain those backup tables. So as a solution, we decided to create a SQL Job that populates the list of unused tables and email the list to the DBA Team for review.

The best way to decommission any table is to rename it first, and if it does not break the functionality of the application, we can drop the table and its dependencies. We decided that after a review of the unused table completes; we will rename the tables and later drop them.

Click through for the techniques and a script which checks tables. It does look fairly reasonable, with the concern being if you restart the SQL Server instance or look at a table which is only accessed at a particular time of year.

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Public Preview of SQL Server on Azure Arc

Sasha Nosov gives us an update on Azure Arc:

The preview includes the following features:

– Use Azure Portal to register and track the global inventory of your SQL instances across different hosting infrastructures. You can register an individual SQL instance or register a set of servers at scale using the same auto-generated script.

– Use Azure Security Center to produce a comprehensive report of vulnerabilities in SQL servers and get advanced, real time security alerts for threats to SQL servers and the OS.

– Investigate threats in SQL Servers using Azure Sentinel 

– Periodically check the health of the SQL Server configurations and provide comprehensive reports and remediation recommendations using the power of Azure Log analytics.

Click through for more information and documentation.

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Stellar Repair: A Review

Grant Fritchey reviews a product which attempts to repair corrupted SQL Server databases:

Let’s start with the most important piece of information you need: it works.

The software itself is really simple to use and just does what you need, repairs your corrupted SQL Server instance. On that alone, I can recommend the tool.

However, there are a few gotchas I ran into along the way. Mostly, little stuff. It’s things a little polish in the UI and some clean up around language could help out. Don’t get me wrong, I’m happy with this software. It worked. It’s just how it works that we should talk about.

Click through for Grant’s full review.

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Automatic Soft NUMA in SQL Server

Ameena Lalani walks us through NUMA and automatic soft NUMA in SQL Server:

Modern processors have multiple cores per socket. Each socket is represented, usually, as a single NUMA node. The SQL Server database engine partitions various internal structures and partitions service threads per NUMA node. With processors containing 10 or more cores per socket, using software NUMA to split hardware NUMA nodes generally increases scalability and performance. Prior to SQL Server 2014 (12.x) SP2, software-based NUMA (soft-NUMA) required you to edit the registry to add a node configuration affinity mask, and was configured at the host level, rather than per instance. Starting with SQL Server 2014 (12.x) SP2 and SQL Server 2016 (13.x), soft-NUMA is configured automatically at the database-instance level when the SQL Server Database Engine service starts. Please read this  documentation and this documentation for more understanding.

Read on for more info.

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Using Synonyms in SQL Server

Greg Larsen takes us through the ins and outs of synonyms in SQL Server:

Once a database object has been created, and lots of application code has been written that references the object, it becomes a nightmare to rename the object. The nightmare comes from the amount of effort and coordination work required to make the name change without the application failing. If just one place is missed when coordinating the rename, the outcome could be disastrous. This is where a synonym can help minimize the risk associated with renaming a base object.

I’ll admit that I don’t really think about synonyms much and have used them at most a couple of times in my career. I can see where they’d be useful, but that comes at the risk of something going wrong and people not even realizing they exist.

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