How to fix Error 4313 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 4313 (Obsolete Backup/Media Marker)

Why This Error Happens

Error 4313 occurs when SQL Server 2025 attempts to read a backup set or media header that is flagged as obsolete, meaning the Log Sequence Number (LSN) chain is broken or the media header does not match what the restore sequence expects. This typically happens due to corrupted backup files, an interrupted backup write operation, or attempting to restore a differential/log backup out of sequence after a full backup was marked obsolete by a newer backup operation. In some cases, this is triggered by mismatched backup software versions interacting with the Windows Server 2025 Volume Shadow Copy Service (VSS) writer for SQL.

Step-by-Step Resolution Guide

Step 1: Verify the Integrity of the Backup Media

  • Run RESTORE VERIFYONLY FROM DISK = 'C:\Backups\YourFile.bak' in SQL Server Management Studio (SSMS) to check if the file is physically corrupted.
  • Check the physical storage path (local disk or network share) for connectivity drops that may have truncated the file during the backup write.
  • Inspect the SQL Server Error Log located at C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG for accompanying I/O errors (such as Error 823 or 824) that often precede a 4313 obsolete marker.

Step 2: Rebuild the Backup Sequence Chain

  • Do not attempt to restore the differential or transaction log backup directly if the preceding Full backup is marked obsolete.
  • Take a fresh, immediate Full backup of the database to establish a new, valid starting point for the LSN chain:
  • BACKUP DATABASE [YourDB] TO DISK = 'C:\Backups\NewFull.bak' WITH INIT
  • If this is a Log Shipping or Always On Availability Group scenario, re-initialize the secondary replica from this new full backup rather than attempting to patch the old chain.

Step 3: Check VSS Writer and Permissions on Windows Server 2025

  • Open Command Prompt as Administrator and run vssadmin list writers to ensure the “SqlServerWriter” status reads as “No error” (stable state).
  • If the writer shows a failed state, restart the SQL Server VSS Writer service via services.msc by locating “SQL Server VSS Writer” and selecting Restart.
  • Ensure the service account running SQL Server has explicit Read/Write NTFS permissions on the backup destination folder to prevent the OS from locking or corrupting the file mid-write.

Step 4: Update SQL Server Cumulative Updates

  • Navigate to the Microsoft Update Catalog and verify you are running the latest Cumulative Update (CU) for SQL Server 2025.
  • Install the update via the standalone installer to patch any known backup/restore engine bugs related to media set validation.
  • Reboot the Windows Server 2025 instance to ensure the SQL Server binaries are fully refreshed.

Alternative or Verification Steps

  • Verification: After creating the new Full backup in Step 2, immediately attempt a test restore to a different database name (e.g., YourDB_Test) using RESTORE DATABASE... WITH MOVE to confirm the chain is no longer obsolete.
  • Alternative: If the native backup file remains unusable, utilize a third-party repair tool specifically designed for .bak file header reconstruction, or restore from an older, verified valid backup set and accept the data loss gap between the corrupted backup and the last known good state.