How to fix Error 12314 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 12314 — “User-Defined Methods Are Not Supported with %S_MSG”

Why This Error Happens

This error occurs when a Common Language Runtime (CLR) integration object, such as a user-defined type (UDT) or user-defined aggregate, attempts to invoke a custom method that SQL Server’s CLR host policy does not permit in the current execution context. It is typically triggered by incompatible assembly permission sets (SAFE, EXTERNAL_ACCESS, or UNSAFE) that restrict method invocation, or by a mismatch between the serialized format of the type and the method being called. Corrupted or improperly registered assemblies in the database, as well as incomplete deployment of the CLR object following an upgrade to SQL Server 2025, can also cause this behavior.

Step-by-Step Resolution Guide

Step 1: Verify CLR Integration is Enabled and Configured Correctly

  • Open SQL Server Management Studio (SSMS) and connect to the affected instance.
  • Run the following to confirm CLR is enabled:
sp_configure 'clr enabled';
  • If the value is 0, enable it:
sp_configure 'clr enabled', 1;
RECONFIGURE;
  • Check the clr strict security setting, as SQL Server 2025 enforces this by default:
sp_configure 'clr strict security';

Step 2: Review and Reassign Assembly Permission Sets

  • Query the current permission set assigned to the problematic assembly:
SELECT name, permission_set_desc FROM sys.assemblies;
  • If the assembly is set to SAFE but the user-defined method requires external resource access, drop and recreate it with the correct permission level:
ALTER ASSEMBLY YourAssemblyName
WITH PERMISSION_SET = EXTERNAL_ACCESS;
  • Ensure the assembly is signed with a certificate or asymmetric key and mapped to a login with the UNSAFE ASSEMBLY permission if UNSAFE access is required.

Step 3: Re-register the CLR Type or Assembly

  • Drop the existing user-defined type/aggregate and the associated assembly:
DROP TYPE YourUDTName;
DROP ASSEMBLY YourAssemblyName;
  • Recompile the .NET assembly against the SQL Server 2025 CLR runtime (verify target framework compatibility in Visual Studio).
  • Re-deploy and re-register the assembly:
CREATE ASSEMBLY YourAssemblyName
FROM 'C:\SQLAssemblies\YourAssembly.dll'
WITH PERMISSION_SET = SAFE;

CREATE TYPE YourUDTName
EXTERNAL NAME YourAssemblyName.[YourClassName];

Step 4: Check Windows Server 2025 / Windows 11 Security Policies

  • Open Local Security Policy (secpol.msc) and confirm the SQL Server service account has “Log on as a service” rights.
  • Verify that Windows Defender Application Control (WDAC) or AppLocker policies are not blocking the CLR assembly DLL located in the SQL Server binary path (typically C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Binn\).
  • Restart the SQL Server service via services.msc or:
Restart-Service -Name 'MSSQLSERVER'

Alternative or Verification Steps

  • Test the fix by executing the stored procedure or query that previously triggered Error 12314, and confirm no exception is raised in the SQL Server error log (ERRORLOG in the Log directory).
  • If the error persists, consider rewriting the user-defined method using standard T-SQL logic instead of CLR integration, or isolate the assembly in a sandboxed test database to confirm whether the issue is environment-specific versus code-specific.