How to fix Error 8800 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 8800 – DOP Feedback Internal Error

Why This Error Happens

This error occurs when SQL Server 2025’s new Degree of Parallelism (DOP) Feedback feature encounters corrupted or inconsistent cached execution plan metadata while attempting to adjust parallelism settings for a recurring query. It typically stems from plan cache corruption, conflicts between Query Store persistence and the DOP feedback telemetry engine, or a mismatch between the plan hash stored in memory and the one persisted to disk. In some cases, this is triggered by an incomplete upgrade/migration where legacy plan cache entries are incompatible with the new DOP Feedback internal structures introduced in SQL Server 2025.

Step-by-Step Resolution Guide

Step 1: Clear the Plan Cache for the Affected Database

  • Open SQL Server Management Studio (SSMS) and connect to the instance reporting the error.
  • Run DBCC FREEPROCCACHE to clear the global plan cache (use with caution in production; schedule during low-traffic windows).
  • For a targeted approach, use DBCC FREEPROCCACHE (plan_handle) after identifying the specific plan hash from the error message via sys.dm_exec_query_stats.

Step 2: Disable and Re-enable DOP Feedback Persistence

  • Navigate to Database Properties → Query Store in SSMS, or run:
  • ALTER DATABASE SCOPED CONFIGURATION SET DOP_FEEDBACK = OFF;
  • Wait for active query plans to flush (typically 60–90 seconds), then re-enable:
  • ALTER DATABASE SCOPED CONFIGURATION SET DOP_FEEDBACK = ON;
  • This forces SQL Server to rebuild the DOP feedback internal tracking structures from scratch.

Step 3: Validate Query Store Integrity

  • Check for corruption in Query Store using:
  • EXEC sp_query_store_consistency_check;
  • If inconsistencies are found, consider running:
  • ALTER DATABASE [YourDB] SET QUERY_STORE CLEAR;
  • Restart the SQL Server service via Services.msc (Windows Server 2025) or net stop MSSQLSERVER && net start MSSQLSERVER in an elevated Command Prompt.

Step 4: Apply the Latest Cumulative Update

  • Check the installed build number: SELECT @@VERSION;
  • Download and apply the latest SQL Server 2025 Cumulative Update (CU) from the Microsoft Update Catalog, as this specific DOP Feedback bug is addressed in post-RTM patches.
  • Reboot the Windows Server 2025 / Windows 11 host after installation to ensure all binaries are correctly replaced.

Alternative or Verification Steps

  • To verify the fix, monitor the SQL Server Error Log (Management → SQL Server Logs in SSMS) for 24–48 hours to confirm Error 8800 no longer appears under load.
  • If the error persists after patching, as a temporary workaround, disable DOP Feedback entirely at the instance level using sp_configure 'dop feedback', 0; followed by RECONFIGURE; until Microsoft issues a permanent hotfix.