How to fix Error 6341 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 6341 – XML Schema Collection Dropped or Altered

Why This Error Happens

This error occurs when a table variable in a batch references a column typed against an XML schema collection, and that schema collection is dropped or altered (via ALTER XML SCHEMA COLLECTION or DROP XML SCHEMA COLLECTION) by another session or a later statement within the same batch before execution completes. Because table variables are bound to the schema definition at compile time, SQL Server cannot reconcile the mid-batch metadata change and invalidates the cached execution plan. This is typically caused by concurrent DDL operations, deployment scripts running out of order, or application code that dynamically modifies XML schema collections while transactions are still active.

Step-by-Step Resolution Guide

Step 1: Identify the Conflicting Session or Script

  • Query sys.dm_exec_requests and sys.dm_tran_locks to check for concurrent sessions executing ALTER XML SCHEMA COLLECTION or DROP XML SCHEMA COLLECTION statements.
  • Review deployment/migration scripts (e.g., DACPAC, SSDT projects) for XML schema collection changes bundled in the same release as table variable usage.
  • Check SQL Server Agent Job history for overlapping jobs that touch the same schema collection name.

Step 2: Re-run the Batch in Isolation

  • Simply re-executing the batch, as the error message suggests, resolves transient cases caused by one-time concurrent DDL.
  • Wrap the batch in SET XACT_ABORT ON; at the top of the script to ensure a clean rollback and retry rather than a partial execution state.
  • If using an application connection pool, ensure the connection is reset (sp_reset_connection) before retry to clear any stale cached plans.

Step 3: Serialize Schema Changes from Data Operations

  • Separate DDL changes (ALTER/DROP XML SCHEMA COLLECTION) into their own deployment window, distinct from scripts that declare and use table variables bound to that collection.
  • In application code, implement a retry-on-error pattern specifically catching Error 6341 (use TRY...CATCH in T-SQL or exception handling in the app layer) with a single automatic re-run.
  • If using CI/CD pipelines (Azure DevOps, GitHub Actions) targeting Windows Server 2025 hosted SQL Server instances, add explicit step ordering/dependencies so schema collection alterations always complete and commit before dependent batches run.

Step 4: Rebuild and Recompile Affected Objects

  • Run sp_recompile on any stored procedures or table variable declarations tied to the affected XML schema collection to force a fresh plan on next execution.
  • If corruption of the schema collection metadata is suspected (rare, but possible after abrupt service termination on Windows Server 2025), run DBCC CHECKDB against the database to rule out catalog corruption.

Alternative or Verification Steps

  • Verify the fix by re-running the original batch during a quiet maintenance window and confirming no Error 6341 appears in SQL Server Error Logs (EXEC xp_readerrorlog 0, 1, N'6341';) or Windows Event Viewer under Applications and Services Logs > MSSQLSERVER.
  • As an alternative, replace the table variable with a temporary table (#TempTable) if the XML schema collection is subject to frequent alteration — temp tables are less sensitive to this specific binding conflict, though you lose some table-variable-specific optimizer behavior.