How to fix Error 9050 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 9050 – Invalid Hyperscale Log Transformation Request

Why This Error Happens

Error 9050 occurs when SQL Server 2025 attempts to transform a database’s transaction log into the Hyperscale log format, but the operation is rejected due to an incompatible database state, such as an active backup, replication, or Always On Availability Group configuration. This can also happen if the log file contains unsupported legacy structures from an older compatibility level, or if the database is not properly provisioned for Hyperscale service tier operations. Additionally, insufficient permissions on the log file directory in Windows Server 2025 can prevent the transformation process from writing the new log structure.

Step-by-Step Resolution Guide

Step 1: Verify Database Compatibility and Service Tier

  • Confirm the database is actually provisioned under the Hyperscale service tier; this transformation does not apply to Standard or General Purpose tiers.
  • Run SELECT compatibility_level FROM sys.databases WHERE name = 'YourDatabaseName'; and ensure it is set to 160 or higher.
  • If the compatibility level is outdated, update it using ALTER DATABASE YourDatabaseName SET COMPATIBILITY_LEVEL = 160;.

Step 2: Check for Blocking Operations

  • Ensure no active full or differential backups are running against the target database, as these lock the log file structure.
  • Query sys.dm_exec_requests to identify any long-running transactions or backup operations.
  • Pause any Always On Availability Group synchronization temporarily using ALTER AVAILABILITY GROUP [AGName] SET (ROLE = SECONDARY); on the affected replica if applicable.

Step 3: Validate File System Permissions

  • Navigate to the SQL Server data directory, typically located at C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\DATA\.
  • Right-click the .ldf log file, select Properties, then Security, and confirm the “NT SERVICE\MSSQLSERVER” account has Full Control.
  • Restart the SQL Server service via services.msc or run net stop MSSQLSERVER && net start MSSQLSERVER in an elevated Command Prompt to reapply permissions.

Step 4: Manually Retry the Log Transformation

  • Detach any monitoring or third-party backup agents temporarily to rule out file locks.
  • Execute the transformation command again using ALTER DATABASE YourDatabaseName SET HYPERSCALE_LOG_FORMAT = ON; (or the equivalent maintenance command provided by your SQL Server 2025 build).
  • Monitor the SQL Server error log located at C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG for confirmation of success.

Alternative or Verification Steps

  • Verify the fix by checking sys.databases for the log_format column (or equivalent Hyperscale metadata view) to confirm it now reflects the Hyperscale format status.
  • If the error persists, restore the database from a pre-transformation backup and open a support case with Microsoft, as the log file may require a repair through DBCC CHECKDB with the REPAIR_ALLOW_DATA_LOSS option as a last resort.