How to fix Error 4081 on Windows Server 2025 / Windows 11

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Why This Error Happens

Error 4081 occurs when SQL Server’s query parser detects that a parameter is being used in a context that implies a table-valued parameter (TVP), but the parameter was either not explicitly declared with a user-defined table type or is being referenced incorrectly within a stored procedure or dynamic SQL batch. This typically stems from a mismatch between the declared parameter type and its actual usage (e.g., passing a scalar variable where a TVP is expected, or vice versa). It can also surface after an in-place upgrade to SQL Server 2025 if legacy T-SQL code relies on deprecated type inference behavior that is now stricter.

Step-by-Step Resolution Guide

Step 1: Identify the Offending Parameter and Procedure

  • Open SQL Server Management Studio (SSMS) and locate the exact stored procedure or batch referenced in the error message.
  • Run the following to find recent compilations that triggered the error:
  SELECT * FROM sys.dm_exec_query_stats
  CROSS APPLY sys.dm_exec_sql_text(sql_handle)
  WHERE text LIKE '%YourProcName%';
  • Confirm whether the parameter in question (%.*ls in the message) is intended to be scalar or table-valued.

Step 2: Correct the Parameter Declaration

  • Open the procedure definition in C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Scripts (or your source-controlled .sql file) and verify the READONLY keyword is present for any TVP:
  CREATE PROCEDURE dbo.MyProc
      @MyTable dbo.MyTableType READONLY
  AS ...
  • Ensure the user-defined table type (dbo.MyTableType) actually exists by checking:
  SELECT * FROM sys.table_types WHERE name = 'MyTableType';
  • If the type is missing or was dropped during migration, recreate it using CREATE TYPE.

Step 3: Rebuild and Recompile the Procedure

  • Force a recompile to clear any cached, outdated execution plans:
  EXEC sp_recompile 'dbo.MyProc';
  • Restart the SQL Server service via Services.msc or PowerShell:
  Restart-Service MSSQLSERVER -Force
  • Re-run the original query/application call that triggered Error 4081.

Step 4: Validate Compatibility Level Settings

  • Check the database compatibility level, as SQL Server 2025 may enforce stricter parsing rules under newer compatibility levels:
  SELECT name, compatibility_level FROM sys.databases WHERE name = 'YourDB';
  • If recently upgraded, temporarily test with a prior compatibility level (e.g., 160) to confirm the error is tied to new parser behavior, then adjust your TVP code to be compliant rather than permanently downgrading.

Alternative or Verification Steps

  • Verify the fix by executing the stored procedure manually in SSMS with a properly structured TVP variable and confirming no Error 4081 is returned.
  • If the issue persists, use SQL Server Profiler or Extended Events to trace the exact execution plan compilation step where the parameter type deduction fails, and compare it against a known-working procedure signature.