How to fix Error 453 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 453 – Collation Restricted to Unicode Data Types Only

Why This Error Happens

Error 453 occurs when a collation designed exclusively for Unicode data types (such as those with _SC, _UTF8, or certain Japanese/Asian collations) is mistakenly assigned at the server or database level instead of at the column level. SQL Server 2025 enforces stricter validation during instance builds, database creation, and restores, rejecting any COLLATE statement that applies a Unicode-only collation outside of nchar, nvarchar, or ntext column definitions. This typically stems from an incorrect setup script, a copy-pasted collation name from a column definition, or a misconfigured answer file used during unattended installation.

Step-by-Step Resolution Guide

Step 1: Identify Where the Invalid Collation Is Being Applied

  • Check the exact command or script that triggered the error (CREATE DATABASE, ALTER DATABASE, or instance setup).
  • Look for collation names containing suffixes like _UTF8, _SC, or _140_SC — these are Unicode-only and invalid at server/database scope.
  • Run the following to confirm the collation’s supported scope:
  SELECT name, description 
  FROM sys.fn_helpcollations() 
  WHERE name = 'YourCollationNameHere';

Step 2: Correct the Database or Server-Level Collation

  • Replace the Unicode-only collation with a standard, general-purpose collation (e.g., SQL_Latin1_General_CP1_CI_AS or Latin1_General_100_CI_AS_SC_UTF8 is not valid here — use a non-Unicode-restricted equivalent).
  • For a new database, use:
  CREATE DATABASE YourDB
  COLLATE SQL_Latin1_General_CP1_CI_AS;
  • For server-level changes during setup, edit the Instance Configuration collation field in SQL Server Setup, or update the SQLCOLLATION parameter in your ConfigurationFile.ini used for unattended installs on Windows Server 2025.

Step 3: Apply the Unicode Collation Only at the Column Level

  • If your intent was to use a Unicode-specific collation (e.g., for multilingual nvarchar data), apply it directly to the column instead:
  ALTER TABLE YourTable
  ALTER COLUMN YourColumn NVARCHAR(100)
  COLLATE Japanese_XJIS_140_SC_UTF8;
  • Ensure the column data type is nchar, nvarchar, or ntext — non-Unicode types (char, varchar) will trigger Error 453 even at the column level.

Step 4: Rebuild or Reconfigure the Instance if Set During Installation

  • If the error occurred during SQL Server 2025 installation, rerun Setup from the installation media on Windows Server 2025 or Windows 11.
  • Navigate to Server Configuration > Collation and manually select a valid non-Unicode-restricted collation from the dropdown instead of typing it manually.
  • Alternatively, use Setup.exe /ACTION=RebuildDatabase /SQLCOLLATION=SQL_Latin1_General_CP1_CI_AS for master database recovery.

Alternative or Verification Steps

  • Run SELECT SERVERPROPERTY('Collation'); and SELECT DATABASEPROPERTYEX('YourDB', 'Collation'); to confirm the applied collation is no longer Unicode-restricted.
  • If the error persists during restore operations, use RESTORE DATABASE ... WITH REPLACE after explicitly specifying a compatible collation in the ALTER DATABASE statement post-restore.