How to fix Error 860 on Windows Server 2025 / Windows 11

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Why This Error Happens

Error 860 typically occurs when SQL Server’s Buffer Pool Extension (BPE) feature encounters an inconsistency between the in-memory buffer descriptor and the actual data stored on the extension file. This is most commonly caused by an unexpected I/O failure, a corrupted BPE cache file, or a mismatch between the database file offset and the extension offset due to a hardware-level write failure. In rare cases, this also surfaces when the underlying SSD/NVMe drive hosting the .bpe file has suffered sudden disconnection or driver-level corruption during peak read activity.

Step-by-Step Resolution Guide

Step 1: Disable and Remove the Corrupted Buffer Pool Extension File

  • Open SQL Server Management Studio (SSMS) and connect to the affected instance.
  • Run the following T-SQL command to disable BPE immediately:
ALTER SERVERCONFIGURATION SET BUFFER POOL EXTENSION OFF;
  • Manually delete the orphaned .bpe file from its storage path (commonly found under D:\SQLCache\ or wherever it was configured).

Step 2: Verify Disk Health and Storage Drivers

  • Open Event Viewer on Windows Server 2025/Windows 11 and check the System log for Disk or Storport errors (Event ID 7 or 153) around the same timestamp as Error 860.
  • Run chkdsk D: /f /r (replace D: with the actual BPE drive letter) during a scheduled maintenance window to repair file system-level corruption.
  • Update storage drivers via Device Manager > Disk Drives > Update Driver, especially if using NVMe RAID controllers.

Step 3: Re-enable Buffer Pool Extension on a Stable Volume

  • Recreate the BPE file on a different, verified-healthy drive using:
ALTER SERVERCONFIGURATION 
SET BUFFER POOL EXTENSION ON 
(FILENAME = 'E:\SQLCache\BPE_Cache.bpe', SIZE = 50 GB);
  • Ensure the SQL Server service account has Full Control permissions on the new folder path (E:\SQLCache\).
  • Restart the SQL Server service via services.msc to apply the configuration.

Step 4: Run DBCC CHECKDB on Affected Database File

  • Identify the Database file id and Database file offset values from the original error message.
  • Run the following command against the specific database to confirm there is no deeper physical corruption:
DBCC CHECKDB ('YourDatabaseName') WITH NO_INFOMSGS, ALL_ERRORMSGS;
  • Review the output for any allocation or consistency errors tied to the reported file ID.

Alternative or Verification Steps

  • Monitor the SQL Server Error Log and Windows Event Viewer for 24-48 hours to confirm Error 860 does not recur after re-enabling BPE.
  • If the error persists even after replacing the BPE file, disable Buffer Pool Extension permanently and rely on physical RAM allocation, as this indicates a deeper hardware-level incompatibility rather than a software corruption issue.