SQL Server 2025 Preview release notes

Applies to: SQL Server 2025 (17.x) Preview

This article describes requirements, limitations, and known issues for SQL Server 2025 (17.x) Preview.

This article is updated for release candidate (RC) 0.

Hardware and software requirements

For hardware and software requirements, see Hardware and software requirements for SQL Server 2025 Preview.

Preview features

Explore preview development features with a new PREVIEW_FEATURES database scoped configuration. Enable PREVIEW_FEATURES to test some features, such as vector indexes. This configuration lets you try select features in preview even after SQL Server reaches general availability. These features will become generally available in future cumulative updates. When a cumulative update provides general availability for a feature, the database-scoped configuration is no longer be necessary for that feature.

To use these features, enable the PREVIEW_FEATURES database scoped configuration.

The following table identifies features originally released as preview their current status:

All other features described in the What's new in SQL Server 2025 Preview article are aligned with the release of SQL Server. They don't require enabling the preview feature database scoped configuration.

For more information, review Opt in for preview features - FAQ.

Known issues

SQL Server 2025 (17.x) Preview has currently identified the following known issues:

• Windows Arm64 not supported
• In-place upgrade fails due to Microsoft Visual C++ Redistributable
• In-place upgrade fails due to replication
• Adding a remote replication distributor fails
• Linked server connections fail after an upgrade
• SQL Server on Windows fails to start on machines with more than 64 logical cores per NUMA node
• Incorrect behavior of SESSION_CONTEXT in parallel plans
• Access violation exception occurs under certain conditions
• Issue when setting the backup compression algorithm to ZSTD
• PolyBase components fail to start
• PolyBase connections fail to external SQL Server source
• SQL Server on Linux fails to start on machines with hybrid CPU architecture
• Linux PolyBase Network encryption enabled fails
• Local ONNX models not supported on Linux operating systems

Windows Arm64 not supported

SQL Server 2025 (17.x) Preview is not supported on Windows Arm64. Only Intel and AMD x86-64 CPUs with up to 64 cores per NUMA node are currently supported.

In-place upgrade fails due to Microsoft Visual C++ Redistributable

An upgrade from the following versions might fail:

• SQL Server 2016 (13.x)
• SQL Server 2017 (14.x)

This can happen when the existing operating system environment is missing the Microsoft Visual C++ Redistributable for Visual Studio 2022, or an older version of this component is installed.

When this happens, the installation log includes an entry like the following example:

This application requires Microsoft Visual C++ Redistributable for
Visual Studio 2022 (x64/x86, version 14.34 at minimum).
Please install the Redistributable, then run this installer again.
For more information, see: https://go.microsoft.com/fwlink/?linkid=2219560.

To complete the upgrade, add or repair the redistributable component, and run the installation again.

To get the redistributable file, review Microsoft Visual C++ Redistributable latest supported downloads.

In-place upgrade fails due to replication

Upgrades to SQL Server 2025 (17.x) Preview from all previous versions of SQL Server might fail if your SQL Server instance:

• Is configured as a replication publisher.
• Has a remote distributor in the replication topology.
• Isn't configured with a trusted certificate.

In this scenario, during the in-place upgrade, the SQL Server replication component shows a status of Failed and you see the following error:

There was an error executing the Replication upgrade scripts. See the SQL Server error log for details.

The SQL Server error log contains the following errors:

OLE DB provider "MSOLEDBSQL19" for linked server "repl_distributor" returned message 
"Client unable to establish connection".
SSL Provider: The certificate chain was issued by an authority that is not trusted.
Error executing sp_vupgrade_replication.

You might see the following behavior after the upgrade:

• Replication continues to succeed but changes to the publication fail.
• Replication Monitor in SQL Server Management Studio (SSMS) fails.
• Agent status in the SSMS UI fails.

You can resolve this issue preemptively before you start the upgrade, or you can resolve the issue after an upgrade fails.

Before starting the upgrade

If you know that your SQL Server upgrade is going to encounter this issue, you can preemptively mitigate the failure by configuring the SQL Server instance to use a public commercial certificate or a certificate from an internal certificate authority.

This is the recommended option for maximum security.

After a failed upgrade

After an upgrade fails, you can still configure the SQL Server instance to use a public commercial certificate or a certificate from an internal certificate authority.

After configuring your SQL Server instance to use a certificate, repair the SQL Server installation.

Alternatively, for SQL Server on Windows, you can choose the less secure option of overriding the secure default of the new OLEDB provider and set TrustServerCertificate=True to trust the self-signed certificate. Customers on Linux can't override defaults, and must import a trusted certificate to resolve this issue.

To override the new default, follow these steps:

1. Use the sys.sp_serveroption stored procedure to set the TrustServerCertificate=Yes option:

   exec sys.sp_serveroption N'repl_distributor', 'provider string', N'TrustServerCertificate=Yes' 
   

2. Set the following Trust Server Certificate registry entry to 1:

   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\SNI19.0\GeneralFlags\Flag2

3. Restart the SQL Server instance.

4. Repair the SQL Server installation to finalize the upgrade.

Adding a remote replication distributor fails

When configuring a distributor for replication, the sp_adddistributor stored procedure fails when:

• The publisher is a SQL Server 2025 (17.x) Preview instance.
• The distributor is remote.
• The distributor isn't configured with a trusted certificate.

You might see the following error when running sp_adddistributor on the publisher instance:

OLE DB provider "MSOLEDBSQL19" for linked server "repl_distributor" returned message
"Client unable to establish connection".
Msg -2146893019, Level 16, State 1, Line 21
SSL Provider: The certificate chain was issued by an authority that is not trusted.

A remote distributor uses a linked server for communication between the publisher and distributor. The new secure default introduced in SQL Server 2025 (17.x) Preview of the new OLEDB provider requires that TrustServerCertificate=False.

To resolve this issue, configure the distributor SQL Server instance to use a public commercial certificate or a certificate from an internal certificate authority.

Linked server connections fail after an upgrade

When you upgrade from previous versions of SQL Server to SQL Server 2025 (17.x) Preview with Microsoft OLE DB Driver 19, existing linked server configurations might fail. Different default values for the encryption parameter might cause this failure unless a valid certificate is provided.

To learn more, review Linked servers.

SQL Server on Windows fails to start on machines with more than 64 logical cores per NUMA node

Issue: SQL Server instances on Windows might fail to start after the installation if the machine has more than 64 logical cores per NUMA node.

For more information, see Limit number of logical cores per NUMA node to 64.

Incorrect behavior of SESSION_CONTEXT in parallel plans

Queries that use the built-in SESSION_CONTEXT function might return incorrect results or trigger access violation (AV) dumps when executed in parallel query plans. This issue stems from the way the function interacts with parallel execution threads, particularly when the session is reset for reuse.

For more information, see the Known issues section in SESSION_CONTEXT.

Access violation exception occurs under certain conditions

When the Optional parameter plan optimization feature encounters a predicate that is based on a LOB column, an access violation exception can occur. A fix has been identified and will be part of the next preview release of SQL Server 2025.

Large object (LOB) data types in the Database Engine can store data that exceeds 8,000 bytes. These data types store data on a row-overflow data page. A LOB also encompasses data types that store data on dedicated LOB page structures, which use a text or image pointer of in-row references to LOB data pages. For more information about data storage, see Pages and extents architecture guide.

Issue when setting the backup compression algorithm to ZSTD

There's a known issue when attempting to set the backup compression algorithm to ZSTD.

When specifying the ZSTD algorithm (backup compression algorithm = 3), the following error message returns:

Msg 15129, Level 16, State 1
Procedure sp_configure '3' is not a valid value for configuration option 'backup compression algorithm'.

Use the new compression algorithm directly in the BACKUP Transact-SQL command instead of setting the server configuration option.

PolyBase components fail to start

PolyBase components can fail to start after upgrading to, or installing a new instance of, SQL Server 2025 (17.x) Preview. Review PolyBase network encryption to learn more.

PolyBase connections fail to external SQL Server source

SQL Server 2025 (17.x) Preview PolyBase connections can fail to external SQL Server sources if the external data source was not properly configured. Review the PolyBase network encryption documentation for more information.

SQL Server on Linux fails to start on machines with hybrid CPU architecture

Issue: SQL Server instances on Linux might fail to start if the machine uses an Intel 12th Gen or later hybrid architecture CPU, and the host operating system is Linux.

You might see an error message similar to the following output:

Reason: 0x00000004 Message: ASSERT: Expression=(result * DrtlGetProcessorCoreCount() == DrtlGetProcessorCount()) File=LibOS\Windows\Kernel\SQLPal\common\dk\sos\src\sosnumap.cpp Line=208

If you want to use a Linux host operating system, you can work around the issue by disabling efficiency cores (E-cores) in your BIOS. If you use containers, or a hypervisor like Hyper-V on Windows (including WSL), you aren't affected.

Linux PolyBase Network encryption enabled fails

On Linux, SQL Server 2025 (17.x) Preview Release Candidate (RC) 0 requires polybase network encryption set to 0.

EXEC sp_configure @configname = 'polybase network encryption', @configvalue = 0;
RECONFIGURE WITH OVERRIDE;

Local ONNX models not supported on Linux operating systems

CREATE EXTERNAL MODEL local ONNX models hosted directly on the SQL Server aren't currently available for Linux on SQL Server 2025 (17.x) Preview RC 0.

Optimized Halloween protection not available

The Optimized Halloween protection feature is not currently available in SQL Server 2025 (17.x) Preview RC 0.

Breaking changes

SQL Server 2025 (17.x) Preview introduces breaking changes to a few SQL Server Database Engine features. To learn more, review Breaking changes in SQL Server 2025 preview.

Build number

Related content

• What's new in SQL Server 2025 Preview