How to fix Error 3003 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 3003 — Differential Backup Based on Multiple File Backups

Why This Error Happens

This error occurs because SQL Server 2025 tracks differential backups against a specific baseline, and that baseline currently spans multiple file or filegroup backups rather than a single full database backup. When you attempt to restore the differential backup, SQL Server detects that the Last LSN (Log Sequence Number) chain requires all corresponding file backups to be restored first, in the correct order, before the differential data can be applied. This typically happens in piecemeal restore scenarios or when file-level backups were taken independently without a unifying full database backup immediately preceding the differential.

Step-by-Step Resolution Guide

Step 1: Identify the Full Backup Chain Using msdb

  • Query the msdb.dbo.backupset table to determine which backups form the baseline for your differential.
  • Run the following T-SQL to inspect the backup history:
SELECT backup_set_id, database_name, type, backup_start_date, file_number
FROM msdb.dbo.backupset
WHERE database_name = 'YourDatabaseName'
ORDER BY backup_start_date;
  • Confirm whether type = 'D' (full) or type = 'F' (file) entries exist as the differential base.

Step 2: Restore All Required File Backups in Sequence

  • Use RESTORE DATABASE ... FILE = 'LogicalFileName' for each file backup identified in Step 1.
  • Ensure you include the NORECOVERY clause so the database remains in a restoring state:
RESTORE DATABASE YourDatabaseName
FILE = 'YourDatabaseName_Data1'
FROM DISK = 'C:\Backups\File1.bak'
WITH NORECOVERY;
  • Repeat this for every file backup listed before attempting the differential restore.

Step 3: Apply the Differential Backup

  • Once all file backups are restored with NORECOVERY, apply the differential backup:
RESTORE DATABASE YourDatabaseName
FROM DISK = 'C:\Backups\YourDiff.bak'
WITH NORECOVERY;
  • If additional transaction logs exist, restore them next using WITH NORECOVERY, finishing with WITH RECOVERY on the final log.

Step 4: Validate File Paths and Backup Device Integrity

  • Check C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Backup\ (or your custom backup path) to confirm no .bak files are missing or corrupted.
  • Use RESTORE VERIFYONLY FROM DISK = 'PathToFile.bak' to validate backup file integrity before restoring.

Alternative or Verification Steps

  • After completing the restore sequence, run RESTORE DATABASE YourDatabaseName WITH RECOVERY; and confirm the database status changes to ONLINE in SQL Server Management Studio (SSMS) under Object Explorer > Databases.
  • If file backups are missing or unrecoverable, consider performing a fresh full database backup immediately to establish a new differential base going forward, avoiding reliance on the incomplete file backup chain.