How to fix Error 5833 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 5833 – Affinity Mask Exceeds Licensed CPU Limit

Why This Error Happens

This error occurs because the ALTER SERVER CONFIGURATION command is attempting to set a CPU affinity mask that includes processor cores beyond what your specific SQL Server 2025 edition is licensed to use. Editions like Standard or Web have hard-coded limits on the number of cores/sockets they can utilize, regardless of how many physical cores exist on the Windows Server 2025 host. This typically happens after a hardware upgrade, a VM resource increase, or a migration where the server now has more logical processors than the SQL Server license tier supports.

Step-by-Step Resolution Guide

Step 1: Verify Your SQL Server Edition and Core Limits

  • Run SELECT SERVERPROPERTY('Edition') in SSMS to confirm your current edition.
  • Cross-reference this with Microsoft’s official “Compute capacity limits by edition” documentation for SQL Server 2025.
  • Note the maximum number of cores/sockets allowed (e.g., Standard Edition is typically capped at the lesser of 4 sockets or 24 cores).

Step 2: Check the Current Affinity Configuration

  • Open a new query window in SQL Server Management Studio (SSMS).
  • Execute EXEC sp_configure 'show advanced options', 1; RECONFIGURE; followed by EXEC sp_configure 'affinity mask'; to view legacy settings.
  • For modern setups, check sys.dm_os_nodes or Server Properties > Processors tab in SSMS to see which CPUs are currently flagged for use.

Step 3: Reset the Affinity Mask to Auto

  • If the mask was manually set incorrectly, reset it to allow SQL Server to auto-manage based on license limits.
  • Run the following T-SQL command to clear the restrictive mask:
  ALTER SERVER CONFIGURATION SET PROCESS AFFINITY MASK = AUTO;
  • Alternatively, right-click the Server instance in SSMS, go to Properties > Processors, and ensure “Automatically set processor affinity mask for all processors” is checked.

Step 4: Manually Align Affinity with Licensed Cores

  • If you need specific cores active (rather than “Auto”), ensure the CPU mask selects a number of cores equal to or less than your license limit.
  • Use the GUI method: In SSMS Server Properties > Processors, manually check boxes only up to your licensed limit (e.g., if licensed for 16 cores, do not check core 17 or higher).
  • Avoid using the deprecated sp_configure 'affinity mask' for systems with more than 32 logical processors, as it uses a bitmask that cannot address higher core counts; use ALTER SERVER CONFIGURATION instead.

Step 5: Restart the SQL Server Service

  • Navigate to SQL Server Configuration Manager.
  • Right-click the SQL Server (MSSQLSERVER) service and select Restart to apply the new affinity configuration.
  • Monitor the SQL Server Error Log immediately following the restart to ensure Error 5833 does not reappear.

Alternative or Verification Steps

  • Verification: After the restart, query SELECT cpu_id, scheduler_id, is_online FROM sys.dm_os_schedulers WHERE status = 'VISIBLE ONLINE'; to confirm the number of active schedulers matches your licensed core count.
  • Alternative Fix: If you require more cores than your current edition allows, you must either upgrade to SQL Server 2025 Enterprise Edition or use Windows Server 2025 Hyper-V to partition the VM/Host to match the exact core count of your SQL license before reapplying the affinity settings.