How to fix Error 3015 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 3015 — “%hs is not yet implemented”

Why This Error Happens

Error 3015 is a placeholder message that SQL Server raises when a specific backup, restore, or media-handling code path has not been fully implemented for the configuration being used — typically triggered during BACKUP or RESTORE operations against unsupported device types, snapshot backups, or preview features in SQL Server 2025. This often occurs when a database is backed up using a feature flag or edition-specific capability (such as an accelerated database recovery snapshot, Azure-integrated backup target, or a new media format) that is only partially rolled out on the installed build. It can also surface when third-party backup tools (VDI/VSS writers) call an internal API surface that Microsoft has reserved but not yet activated in that Cumulative Update.

Step-by-Step Resolution Guide

Step 1: Identify the Exact Operation Triggering the Error

  • Check the SQL Server Error Log at C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG for the full message context surrounding Error 3015.
  • Note whether the error occurs during BACKUP DATABASE, RESTORE, VSS Writer snapshot requests, or a specific T-SQL command — this narrows down which feature is unimplemented.
  • Run SELECT SERVERPROPERTY('ProductVersion'), SERVERPROPERTY('ProductBuild'); to confirm your exact build number.

Step 2: Apply the Latest Cumulative Update (CU)

  • Navigate to Microsoft’s official SQL Server 2025 update catalog and download the latest CU for your build.
  • Install via elevated PowerShell: Setup.exe /Action=Patch /IAcceptSQLServerLicenseTerms /Quiet /InstanceName=MSSQLSERVER.
  • Many “%hs is not yet implemented” errors are resolved in subsequent CUs as Microsoft finalizes preview features (especially around new backup compression algorithms or object storage targets).

Step 3: Disable or Bypass the Unsupported Feature Flag

  • Open SQL Server Configuration Manager and check if a trace flag (e.g., -T flags tied to preview backup engines) is enabled under SQL Server Service properties → Startup Parameters.
  • Remove any experimental trace flags by editing the startup parameters field and removing entries like -T9999 (example placeholder flag) that enable unreleased functionality.
  • Restart the SQL Server service: Restart-Service -Name 'MSSQLSERVER' -Force.

Step 4: Switch to a Fully Supported Backup/Restore Method

  • If the error occurs during a snapshot-based or cloud-tiered backup, revert to standard native backup syntax: BACKUP DATABASE [YourDB] TO DISK = 'C:\Backups\YourDB.bak' WITH COMPRESSION, CHECKSUM;
  • Avoid using WITH SNAPSHOT or Azure Blob integrated backup URLs until the feature is confirmed GA (Generally Available) in your specific build via Microsoft’s release notes.

Step 5: Validate Third-Party Tooling Compatibility

  • If using a third-party VSS-based backup agent (e.g., Veeam, Commvault), confirm the vendor has certified support for SQL Server 2025 — outdated VDI DLLs often call deprecated or unimplemented internal interfaces.
  • Update the backup agent to the latest version and re-run the backup job through the vendor’s native SQL Server plugin rather than generic VSS snapshotting.

Alternative or Verification Steps

  • Run a manual test backup and restore cycle (BACKUP DATABASE → RESTORE VERIFYONLY) on a non-production database to confirm the error no longer appears after applying the CU and removing trace flags.
  • If the error persists after patching, open a Microsoft support case referencing the exact ERRORLOG snippet — Error 3015 is often tied to a specific internal bug ID tracked only through official support channels for newly released SQL Server versions.