Executive Summary & Key Findings

SQL Server 2025 is more than an update; it's a strategic realignment. While new AI and cloud features are exciting, the real story for DBAs and developers lies in what's being removed and changed. Here are the three most critical takeaways for your migration planning.

The 'Why': Microsoft's Strategic Vision for SQL Server

The changes in SQL Server 2025 aren't random; they are deliberate steps in a larger strategy. Microsoft is evolving its flagship database from a self-contained, on-premises engine into a secure, highly interconnected endpoint within a broader hybrid data fabric.

Understanding the Lifecycle: Deprecated vs. Discontinued

To effectively plan your migration, it's crucial to understand Microsoft's terminology. These terms have distinct technical meanings and carry different levels of urgency and risk.

Discontinued Functionality: The End of the Line

SQL Server 2025 completely removes four features, signaling a strategic shift towards Microsoft Fabric. Any code relying on these will fail. Here's what's gone and what to use instead.

The Legacy of Deprecation: Your Technical Debt Deadline

SQL Server 2025 deprecates no new features, but it solidifies the list from previous versions. This is your final call to action to remediate these features before they are potentially removed. Use the filters below to explore by category.

Risk of Inaction: A Visual Breakdown

The chart below visualizes the number of key deprecated features by their risk level. High-risk items, like Database Mirroring, represent a potential loss of critical functionality and should be your top priority.

Proactive Auditing: How to Find Deprecated Features

Don't wait for an upgrade to break your code. SQL Server provides powerful built-in tools to proactively identify the use of deprecated features. Here are two primary methods to audit your instances.

Method 1: Performance Counters (The Quick Scan)

This method gives you a fast, quantitative summary of which deprecated features have been used since the last server restart. Run the following T-SQL query to get an immediate, actionable list.

SELECT
    [object_name],
    [instance_name] AS [Feature],
    [cntr_value] AS [UsageCount]
FROM
    sys.dm_os_performance_counters
WHERE
    [object_name] LIKE N'%SQL%Deprecated Features%'
    AND [cntr_value] > 0
ORDER BY
    [UsageCount] DESC;

Method 2: Extended Events (The Deep Dive)

For more granular, real-time monitoring, Extended Events are the modern solution. They can tell you not just *what* was used, but *who* used it, from *where*, and the *exact T-SQL statement* they ran.

Configure an Extended Events session to capture these two key events:

• deprecation_announcement: Fires the first time a deprecated feature is used in a session.
• deprecation_final_support: Fires when a feature is used that will be removed in the very next major version.

This contextual information is invaluable for pinpointing the exact source of deprecated code, making remediation much faster.

Critical Breaking Changes: The Real Upgrade Risk

The most immediate danger in a SQL Server 2025 migration isn't what's removed, but fundamental shifts in default behavior. These can cause unexpected failures in applications, automation, and even the upgrade process itself.

The Client Provider Revolution

The "Encrypt by Default" Mandate

The new `Microsoft.Data.SqlClient` provider changes a critical default: `Encrypt` is now `True`. This means all connections will attempt to use TLS encryption and validate the server's certificate, which can lead to widespread failures in unconfigured environments.

Impact Analysis: Who is Affected by the Client Provider Change?

This isn't just a database-level change; it's an ecosystem-wide update. The move to `Microsoft.Data.SqlClient` will require code changes across your entire data stack. Here’s a breakdown of the key areas you'll need to remediate.

Breaking Changes: At-a-Glance Summary

In-Place Upgrade Blockers & Known Issues

Forewarned is forearmed. The SQL Server 2025 Preview release notes identify several specific issues that can halt an in-place upgrade. Be aware of these potential roadblocks before you begin.

The Ultimate SQL Server 2025 Migration Checklist

Use this interactive checklist to track your progress through the four critical phases of migration. A systematic approach is key to a successful, low-risk upgrade.

Your 4-Phase Migration Roadmap

A successful transition to SQL Server 2025 requires a proactive, multi-phased strategy. Follow this roadmap to minimize risk and ensure a smooth deployment.