How to fix Error 2733 on Windows Server 2025 / Windows 11

by

Troubleshooting Guide: Error 2733 – “The %ls data type is invalid for return values”

Why This Error Happens

This error occurs when a Transact-SQL user-defined function (UDF) or stored procedure attempts to return a data type that SQL Server does not permit as a valid return value, such as TEXT, NTEXT, IMAGE, CURSOR, or TABLE in unsupported contexts. It is typically triggered during the compilation or deployment of a CLR assembly or T-SQL module where the RETURNS clause references a deprecated or restricted type. This can also surface after an upgrade to SQL Server 2025 if legacy database objects relied on data types that have since been fully deprecated or restricted in return-value scenarios.

Step-by-Step Resolution Guide

Step 1: Identify the Offending Object

  • Open SQL Server Management Studio (SSMS) and locate the exact function or procedure referenced in the error message (check the Activity Log at C:\Program Files\Microsoft SQL Server\160\Setup Bootstrap\Log\Summary.txt if it occurred during setup).
  • Run the following query to scan for deprecated return types across your database:
SELECT o.name, t.name AS return_type 
FROM sys.objects o 
JOIN sys.parameters p ON o.object_id = p.object_id 
JOIN sys.types t ON p.user_type_id = t.user_type_id 
WHERE p.parameter_id = 0 AND t.name IN ('text','ntext','image');

Step 2: Modify the Return Data Type

  • Edit the CREATE FUNCTION or CREATE PROCEDURE script to replace the invalid type with a modern, supported equivalent:
  • Replace TEXT with VARCHAR(MAX).
  • Replace NTEXT with NVARCHAR(MAX).
  • Replace IMAGE with VARBINARY(MAX).
  • Save the script and redeploy using sqlcmd -i "C:\Scripts\FixFunction.sql".

Step 3: Rebuild the CLR Assembly (If Applicable)

  • If the error stems from a .NET CLR integration function, open the project in Visual Studio 2025.
  • Update the C# or VB.NET method signature to map to a SQL-compatible SqlDbType (e.g., change SqlDbType.Text to SqlDbType.NVarChar).
  • Recompile the DLL and redeploy using ALTER ASSEMBLY or re-run the deployment wizard.

Step 4: Clear Cached Execution Plans

  • Once the object is corrected, clear the procedure cache to ensure Windows Server 2025 isn’t reading a stale, invalid plan.
  • Execute DBCC FREEPROCCACHE; in a new query window to force SQL Server to recompile all stored procedures.

Alternative or Verification Steps

  • Verification: Execute the specific function using SELECT dbo.YourFunctionName() or run EXEC sp_helptext 'YourProcName' to confirm the schema now reflects the updated data type without throwing Error 2733.
  • Alternative: If modifying the original object is not feasible immediately, create a wrapper stored procedure that casts the output of the legacy function into a supported data type (e.g., CAST(dbo.OldFunction() AS NVARCHAR(MAX))) before returning it to the client application.