How to fix Error 3873 on Windows Server 2025 / Windows 11

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Why This Error Happens

Error 3873 is typically raised when SQL Server 2025 initializes the Hybrid Buffer Pool feature on a database that contains memory-optimized filegroups or metadata-only memory-optimized objects. This occurs because the MEMORY_OPTIMIZED_DATA filegroup exists but the engine detects that persisted memory-optimized tables are limited to schema-only or metadata structures, triggering a hybrid paging state instead of a fully resident in-memory OLTP configuration. It is often accompanied by misconfigured hybrid_buffer_pool database-scoped configurations or insufficient buffer pool memory allocation on the host.

Step-by-Step Resolution Guide

Step 1: Verify Hybrid Buffer Pool Configuration State

  • Open SQL Server Management Studio (SSMS) or Azure Data Studio connected to the SQL Server 2025 instance.
  • Run the following query to check the current scoped configuration:
  SELECT name, value, value_for_secondary 
  FROM sys.database_scoped_configurations 
  WHERE name = 'HYBRID_BUFFER_POOL';
  • Confirm whether the value is set to 1 (ON) unintentionally for a database with minimal memory-optimized workload.

Step 2: Adjust Database-Scoped Configuration

  • If hybrid buffer pooling is not required for your workload, disable it explicitly at the database level:
  ALTER DATABASE SCOPED CONFIGURATION SET HYBRID_BUFFER_POOL = OFF;
  • Apply the change and restart the specific user database context (not the full instance) using:
  ALTER DATABASE [YourDatabaseName] SET OFFLINE;
  ALTER DATABASE [YourDatabaseName] SET ONLINE;

Step 3: Validate Memory-Optimized Filegroup Paths

  • Navigate to the physical file path defined for the MEMORY_OPTIMIZED_DATA filegroup (commonly under C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\DATA\).
  • Ensure the folder is not pointing to a network share or a drive with restricted I/O, as this can force the engine into a hybrid fallback state.
  • Confirm the Windows Server 2025 service account (NT Service\MSSQLSERVER or custom domain account) has Full Control permissions on this directory via File Explorer > Properties > Security.

Step 4: Restart the SQL Server Service

  • Open Services.msc on Windows Server 2025 or Windows 11.
  • Locate SQL Server (MSSQLSERVER), right-click, and select Restart.
  • Monitor the SQL Server Error Log immediately after restart to confirm Error 3873 does not recur during database recovery.

Alternative or Verification Steps

  • To verify the fix, re-run the sys.database_scoped_configurations query from Step 1 and confirm HYBRID_BUFFER_POOL reflects the intended value (OFF or ON as required) with no corresponding entry in the SQL Server Error Log upon the next database startup.
  • If the message persists despite configuration changes, treat it as informational rather than a failure state—Error 3873 is often logged as a benign status notification confirming hybrid memory handling is active, and can be safely filtered out of Event Viewer alerts if the hybrid buffer pool behavior is intentional for your workload.