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Category: Error Handling

Troubleshooting Network-Related or Instance-Specific Error

Published 2025-07-08 by Kevin Feasel

Aaron Bertrand has started a new series:

This is the first in a series of articles meant to provide practical solutions to common issues. In this post, we’ll talk about one of the most pervasive error messages out there:

A network-related or instance-specific error occurred while establishing a connection to SQL Server. Verify that the instance name is correct and that SQL Server is configured to allow remote connections.

Read on to see what a variety of potential solutions to this problem. I was going to joke “It’s always DNS” but Aaron actually has a section on DNS in there.

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SQL Server Error Log Tips

Published 2025-07-07 by Kevin Feasel

Kevin Hill notes that the error log isn’t just for errors:

SQL Server’s Error Logs often get overlooked, until something breaks. But if you know how to use them, they can tell you what went wrong before you’re knee-deep in outage mode.

Whether you’re a sysadmin who inherited SQL or an MSP juggling multiple environments, understanding the ErrorLog is low effort, high return.

Let’s decode the basics.

Click through for examples of information you can find in the error log. Kevin mentions cycling the error log weekly. Back in my DBA days, I’d cycle them daily because I didn’t want the files to grow too large and become unwieldy. Some of this, of course, depends upon how hard people are pushing that box and how much you need to log.

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Upsert Patterns and Duplicate Keys in T-SQL

Published 2025-06-30 by Kevin Feasel

Ajay Dwivedi runs into an error:

I work with developers quite a lot. There are scenarios where data is received from various sources in an application, and asynchronously pushed to database in multiple sessions/connections.

There are situations where concurrency and transaction speed is high enough to cause below UPSERT code blocks to fail with error message like Cannot insert duplicate key row in object dbo.person with unique index ‘pk_person’

Click through for one way to do things. I will note that Ajay has concerns about the MERGE operator, but Hugo Kornelis took a deep dive into all of the known problems in MERGE and found that most of them were fixed. Hugo’s post does make it clear when using MERGE is a bad idea, as there are still some situations in which it won’t work effectively, but for something like this, it would be fine.

I’ll say that I’m generally not a fan of app locking. There are specific circumstances in which it’s the best answer, but those are rare. Here, I’d rather just use a ROWLOCK table hint or change the serialization level.

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The Costs of Implicit Conversion

Published 2025-06-27 by Kevin Feasel

Andy Brownsword changes things around:

Implicit conversion happens in SQL Server when the engine detects a mismatch in data types and automatically converts from one type to another. This can be helpful as it makes different types interchangeable and is generally transparent to the client, but it can come with issues.

Usually the downside from implicit conversion is seen through performance impact. But we’ve got something a little different today – an inconsistent result set.

Read on for Andy’s example.

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Building a Better Trigger

Published 2025-06-19 by Kevin Feasel

Steve Jones is done with mousetraps:

This seemed to work, but did it really?

The Problem

Let’s illustrate the big problem with this change. I’ll run this code:

Steve hit on one of the problems in trigger design, but there’s another problem that we often see. Steve’s code doesn’t have this problem, but quite often, people assume that rows update one at a time. But if you write a T-SQL UPDATE statement that affects five rows, the trigger fires once for all five. Steve correctly uses the inserted and deleted pseudo-tables to handle all changes, rather than just assuming a single row.

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Troubleshooting Weird Issues

Published 2025-06-11 by Kevin Feasel

Chad Callihan says sometimes, the best answer is not to play the game:

After some database infrastructure changes related to phasing out the use of linked servers, I encountered issues with a setup tool used to build out new databases and other related features. One section of the tool was failing, and the errors indicated that there were still stored procedures utilizing linked servers, which was causing the problem. I asked myself a few questions on how best to proceed. Does the setup tool need to be updated? Do the related database procedures using linked servers need to be updated? Do the linked server changes made need to be rolled back altogether?

Read on for a proper Gordian Knot solution.

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When All AG Nodes are Secondaries

Published 2025-06-09 by Kevin Feasel

Randy Knight demands quorum:

If you’ve encountered a situation where none of your SQL Server Always On Availability Group (AG) replicas become PRIMARY after a cluster failure — you’re not alone.  We recently had a customer with this exact scenario (AG won’t become primary after force quorum), and it is both uncommon and difficult to troubleshoot so I thought it would be worth posting about.

Click through for the scenario, what’s happening, and how to resolve this.

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Split-Brain Scenarios in PostgreSQL Clusters

Published 2025-06-02 by Kevin Feasel

Semab Tariq knows that an application cannot serve two masters:

In this blog post, we will try to explore a critical failure condition known as a split-brain scenario that can occur in PostgreSQL HA clusters. We will first see what split-brain means, and then how it can impact PostgreSQL clusters, and finally discuss how to prevent it through architectural choices and tools available in the PostgreSQL ecosystem

Click through for an explanation of split-brain and what can cause this problem. Additionally, Semab includes several tips on how to limit the likelihood of a split-brain scenario occurring.

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sqlcmd in SQL Server 2025 and Certificate Chain Not Trusted

Published 2025-05-27 by Kevin Feasel

Vlad Drumea points out a new thing to keep an eye on:

SQL Server 2025 provides ODBC sqlcmd version 17 which enforces an encrypted connection.

If you’re trying to use it to connect to instances that don’t have a CA-signed certificate or where TLS encryption was never properly configured, sqlcmd will throw the famous “certificate chain not trusted” error message:

Sqlcmd: Error: Microsoft ODBC Driver 18 for SQL Server : SSL Provider: The certificate chain was issued by an authority that is not trusted.
Sqlcmd: Error: Microsoft ODBC Driver 18 for SQL Server : Client unable to establish connection.

The proper answer to this is to get trusted certificates. The workaround is what Vlad describes, so click through for that.

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