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Applies to: 
SQL Server 2025 (17.x) Preview
This article describes requirements, limitations, and known issues for SQL Server 2025 (17.x) Preview.
Hardware and software requirements
For hardware and software requirements, see SQL Server 2025: Hardware and software requirements.
Known issues
SQL Server fails to start after installation
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.
Upgrade in place
SQL Server 2025 (17.x) Preview doesn't support in place upgrades from previous versions of SQL Server, including SQL Server 2025 CTP releases.
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.
Incorrect behavior of SESSION_CONTEXT in parallel plans
Queries that use the built-in SESSION_CONTEXT function may return incorrect results or trigger access violation (AV) dumps when executed in parallel query plans. This issue stems from the way SESSION_CONTEXT interacts with parallel execution threads, particularly when the session is reset for reuse.
For more information, see the Known issues section in SESSION_CONTEXT.
Build number
| Build | Version number | Date |
|---|---|---|
| Preview | 17.0.700.9 | May 19, 2025 |