How to fix Error 8390 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 8390 – Deprecated ‘::’ Function Calling Syntax

Why This Error Happens

This error occurs because SQL Server 2025 continues its deprecation path for the legacy ::function_name() calling convention used to invoke system/meta-data functions, which was marked deprecated in earlier versions and is now flagged more aggressively via Error 8390. The root cause is almost always legacy T-SQL code, stored procedures, views, or application-generated queries that still reference built-in functions using the old ::fn_helper() style instead of the fully schema-qualified sys.fn_helper() syntax. This is not a permissions or connectivity issue — it is purely a backward-compatibility warning that signals code will break once the syntax is fully removed in a future SQL Server release.

Step-by-Step Resolution Guide

Step 1: Identify All Instances of the Deprecated Syntax

  • Query the SQL Server error log or use Extended Events to capture when Error 8390 fires, since it’s often logged as a warning rather than a hard failure.
  • Search your codebase (stored procedures, functions, views, triggers, SSIS packages, and application connection strings) for the pattern :: immediately preceding a function name, e.g., ::fn_sqlvarbasetostr().
  • Use a script against sys.sql_modules to scan for the literal string '::' combined with common system function names like fn_trace_gettable, fn_virtualfilestats, or fn_sqlvarbasetostr.

Step 2: Replace ‘::’ Syntax with ‘sys.’ Schema-Qualified Calls

  • Edit each identified object and change the calling convention from ::function_name(args) to sys.function_name(args).
  • Example fix: change SELECT * FROM ::fn_helpcollations() to SELECT * FROM sys.fn_helpcollations().
  • Re-deploy or re-compile the modified stored procedures, views, and functions in a test environment first.

Step 3: Update Database Compatibility Level and Validate

  • Confirm the database compatibility level under Database Properties > Options > Compatibility Level in SQL Server Management Studio (SSMS), or run ALTER DATABASE [YourDB] SET COMPATIBILITY_LEVEL = 170; for SQL Server 2025 alignment.
  • Re-run the previously flagged queries/procedures to confirm Error 8390 no longer appears in the output or logs.
  • Check any third-party tools, ORM-generated SQL, or legacy linked-server queries that might still inject the old syntax dynamically.

Step 4: Audit and Patch Application-Level Code

  • Review application source code (C#, Java, Python, etc.) for embedded raw SQL strings containing :: function calls.
  • Update deployment scripts, Entity Framework migrations, or Liquibase/Flyway change sets that may regenerate the deprecated syntax on each release.
  • Push corrected code through your CI/CD pipeline and run integration tests against a staging SQL Server 2025 instance.

Alternative or Verification Steps

  • Enable SQL Server’s Deprecation Features Extended Event (sqlserver.deprecation_announcement) and monitor for any residual triggers of Error 8390 over a 24–48 hour production-like workload.
  • If immediate code remediation isn’t feasible, use sp_configure with trace flags only as a temporary stopgap for monitoring, but note that suppressing the warning does not prevent future removal — full syntax migration to sys. is the only permanent fix.