SQL Server 2025 is here, and if you’re a DBA or IT manager planning an upgrade, you need to know this: Microsoft didn’t just add features: they made some serious breaking changes that could take your production environment offline if you’re not prepared.
I’ve been working with SQL Server since the early days, and this release brings some of the most significant compatibility shifts we’ve seen in years. The good news? Most of these issues are totally manageable if you know what’s coming. Let’s dive into the seven breaking changes that could bite you during your upgrade.
1. Encryption by Default: Your Connections Just Got Locked Down
Here’s the big one that’s catching everyone off guard: SQL Server 2025 now defaults to Encrypt=True for all connections. That means if your applications, SSIS packages, or automation scripts don’t explicitly support encrypted connections, they’ll fail. Period.
This isn’t a suggestion or a best practice anymore: it’s the default behavior. Any legacy application using unencrypted connection strings will start throwing connection errors the moment you flip the switch to 2025.
What you need to do: Audit every connection string in your environment. Look for hardcoded connections in:
- Application config files
- SSIS packages
- PowerShell scripts
- Third-party monitoring tools
- ETL processes
You’ll need to either add Encrypt=True explicitly to your connection strings or configure proper TLS certificates on your SQL Server instances. No shortcuts here.
2. Stricter TLS Validation for Linked Servers
If you’re running linked servers (and let’s be honest, most enterprise environments are), you’re going to hit this one. SQL Server 2025 enforces stricter TLS validation, which means your TrustServerCertificate settings might not cut it anymore.
The old “just trust everything” approach? Gone. Microsoft is pushing everyone toward properly configured certificates, and linked servers are where this gets real.
The fix: You have two options:
- Deploy proper, validated TLS certificates across all your linked server endpoints
- Explicitly set
TrustServerCertificate=Truein your linked server configurations (not recommended for production, but sometimes necessary for dev/test environments)
This is one of those changes where our SQL Server Managed Services team has been helping clients get ahead of the curve. Certificate management across a multi-server environment is tedious work, and missing even one linked server can cascade into major integration failures.
3. Driver Shift: Time to Abandon System.Data.SqlClient
Microsoft is officially moving away from the legacy System.Data.SqlClient driver in favor of Microsoft.Data.SqlClient. If your SSIS packages, custom .NET applications, or automation scripts are still using the old driver, SQL Server 2025 is your wake-up call.
The legacy driver won’t receive updates, bug fixes, or security patches moving forward. You’re essentially running on borrowed time.
What breaks: SSIS packages are particularly vulnerable here. Many older packages use the legacy driver under the hood, and you might not even realize it until things start failing post-upgrade.
Action items:
- Update all custom .NET code to reference
Microsoft.Data.SqlClient - Rebuild and redeploy SSIS packages using the new driver
- Test, test, and test again: especially if you’re using connection pooling or complex authentication scenarios
4. Hardware Hurdles: The >64 Cores Problem
Here’s a weird one that caught us by surprise during early testing: SQL Server 2025 has installation issues on hardware with more than 64 cores per CPU socket.
If you’re running on high-density hardware (think modern AMD EPYC or Intel Xeon processors with crazy core counts), you might hit installation failures or performance degradation. Microsoft is aware of it, but it’s still a documented limitation as of the initial release.
Workaround: You may need to temporarily disable cores during installation or work with Microsoft support to configure proper NUMA node settings. This isn’t something most DBAs deal with regularly, so plan extra time if you’re on modern, high-core-count hardware.
5. Feature Removal: Goodbye MDS and DQS
This is a big one for organizations that invested heavily in Microsoft’s data quality tooling. Master Data Services (MDS) and Data Quality Services (DQS) are completely removed from SQL Server 2025.
No deprecation warning, no “legacy support mode”: just gone.
If you’re using these features, you need an exit strategy before upgrading. Microsoft is pushing users toward Azure Purview and other cloud-based data governance solutions, but that’s not always a simple migration path.
Your options:
- Migrate to third-party master data management tools
- Move to Azure Purview (if you’re cloud-ready)
- Maintain a separate SQL Server 2022 instance specifically for MDS/DQS workloads
This is one of those changes where careful planning is non-negotiable. You can’t roll back from 2025 to 2022 easily once you’ve committed to the upgrade.
6. Full Text Search: The 25MB Document Limit
Full Text Search is still alive and well in SQL Server 2025, but there’s a new caveat: documents larger than 25MB won’t be indexed. They’ll simply be skipped with a warning entry in the error log.
If your organization indexes large PDFs, CAD files, or other document types that regularly exceed 25MB, you’ll have indexing gaps immediately after upgrading.
Mitigation strategies:
- Pre-scan your Full Text catalogs to identify oversized documents
- Implement document splitting or chunking for large files
- Consider moving large document indexing to Azure Cognitive Search or another dedicated search platform
This isn’t necessarily a dealbreaker, but it’s one of those “silent failures” that can go unnoticed for weeks until someone complains that search results are incomplete.
7. Performance Tuning: PSPO and Query Store Conflicts on Secondaries
Finally, we’ve got a performance and stability issue that’s hitting Always On Availability Group configurations. Parameter Sensitivity Plan Optimization (PSPO) can conflict with Query Store on secondary replicas, causing plan instability and unexpected performance degradation on read-only workloads.
This is particularly painful if you’re using readable secondaries for reporting or offloading read traffic from your primary replica.
What we’re seeing:
- Query plans on secondaries don’t match the primary
- Unexpected performance regressions for read-only queries
- Query Store overhead increases on secondaries
Microsoft is working on optimizations, but for now, you may need to disable PSPO on databases with heavy read-only secondary usage or carefully monitor query performance after the upgrade.
This is exactly the kind of issue our Database Health Monitor picks up on automatically. Post-upgrade performance monitoring is critical, and having baseline metrics from before the upgrade makes troubleshooting these kinds of problems dramatically easier.
Your Upgrade Strategy Starts Here
SQL Server 2025 brings incredible performance improvements, new features, and better security defaults: but only if you navigate these breaking changes successfully.
The worst-case scenario? You upgrade on a Friday afternoon, hit one of these issues, and spend your weekend rolling back changes while your applications are offline. We’ve seen it happen, and it’s never fun.
Here’s what we recommend:
Run a comprehensive assessment using SSMS 22 with the Hybrid & Migration component. It’ll automatically flag most of these breaking changes.
Build a detailed compatibility matrix for your specific environment. Every organization is different: know your unique risk areas.
Test in a non-production environment first. This sounds obvious, but you’d be surprised how many shops skip this step under time pressure.
Plan for rollback scenarios. Hope for the best, prepare for the worst.
If you’re looking at this checklist and feeling overwhelmed, you’re not alone. SQL Server upgrades have always been complex, but 2025’s breaking changes add layers of risk that many teams aren’t prepared to handle.
That’s exactly why we built our SQL Server Managed Services offering: to take the stress and risk out of major version upgrades. Our team handles everything from pre-upgrade assessments to post-upgrade performance monitoring, so you can focus on your business instead of troubleshooting connection failures at 2 AM.
Ready to start planning your SQL Server 2025 upgrade the right way? If you want expert help upgrading and maintaining your SQL Servers—patching, performance tuning, backups, monitoring, and the day-to-day DBA work—reach out to us at Stedman Solutions. We’ll help you upgrade with confidence and keep things running smoothly long after the cutover.