How to fix Error 2275 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 2275 – “Unterminated XML Declaration”

Why This Error Happens

Error 2275 occurs when SQL Server’s XML parser encounters an XML declaration (<?xml version="1.0"?>) that is improperly closed or malformed within a column, parameter, or FOR XML/OPENXML operation. This is typically caused by corrupted or truncated XML data being inserted into an xml-typed column, improper string concatenation that splits the declaration tag, or encoding mismatches (e.g., UTF-16 vs UTF-8) during data import. It can also surface after an in-place upgrade to SQL Server 2025 if legacy XML data was stored using deprecated parsing leniencies no longer supported by the updated XML engine.

Step-by-Step Resolution Guide

Step 1: Identify the Offending Query or Data Source

  • Check the SQL Server Error Log (C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG) for the exact statement or stored procedure that triggered Error 2275.
  • Run SELECT * FROM sys.dm_exec_query_stats cross-referenced with sys.dm_exec_sql_text to pinpoint the query handle associated with the failure timestamp.
  • If the error originates from an application (e.g., .NET app on Windows 11 client), enable SQL Profiler or Extended Events to capture the exact XML payload being sent.

Step 2: Validate and Repair the XML Payload

  • Extract the raw XML string from the source (file, API response, or database column) and validate it using a tool like xmllint --noout file.xml or Visual Studio’s XML Editor.
  • Look specifically for truncated declarations, such as <?xml version="1.0 missing the closing ?>.
  • If the data is being concatenated in T-SQL, ensure you are not splitting the declaration tag:
  SET @xmlData = '<?xml version="1.0" encoding="UTF-8"?>' + @BodyContent;
  • If importing via OPENROWSET(BULK...), verify the SINGLE_CLOB or SINGLE_BLOB option matches the actual file encoding.

Step 3: Correct Encoding Mismatches

  • Navigate to the file source properties (right-click file in Windows 11/Server 2025 Explorer > Properties) or check the HTTP header Content-Type of the data source.
  • Ensure the encoding declared in the XML header (e.g., encoding="UTF-8") matches the actual byte-order-mark (BOM) of the file.
  • In SQL Server Management Studio (SSMS), re-save the script or import file using the correct encoding via File > Save As > Save with Encoding.

Step 4: Update SQL Server 2025 Cumulative Updates

  • Open PowerShell as Administrator and check your current build version:
  SELECT @@VERSION;
  • Navigate to the Microsoft Update Catalog and apply the latest Cumulative Update (CU) for SQL Server 2025, as early releases had a known regression in the sqllang.dll XML parsing module.
  • Restart the SQL Server service via services.msc or net stop MSSQLSERVER && net start MSSQLSERVER after patching.

Alternative or Verification Steps

  • Verify the fix: Re-run the original INSERT/UPDATE statement or application transaction that triggered the error; confirm success by querying the table with SELECT ISNULL(TRY_CAST(XmlColumn AS XML), 'Invalid') FROM YourTable to ensure no NULLs are returned for invalid casts.
  • Alternative workaround: If immediate resolution isn’t possible, wrap the insertion logic in a TRY_CAST or TRY_CONVERT function to gracefully handle malformed XML and log rejected rows to a quarantine table instead of halting the transaction.