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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.
This article is updated for community technology preview (CTP 2.1).
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.
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.
Build number
| Build | Version number | Date |
|---|---|---|
| Preview (CTP 2.1) | 17.0.800.3 | June 16, 2025 |
| Preview (CTP 2.0) | 17.0.700.9 | May 19, 2025 |