How to fix Error 5278 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 5278 — DBCC Internal Database Snapshot LSN Mismatch

Why This Error Happens

Error 5278 occurs when DBCC commands (such as DBCC CHECKDB) create an internal database snapshot to perform consistency checks, but encounter a page whose Log Sequence Number (LSN) exceeds the current end of the transaction log. This typically indicates I/O subsystem instability, a crash-consistent but corrupted sparse file backing the snapshot, or concurrent write activity that outpaces the snapshot’s point-in-time view due to underlying storage driver issues. It can also surface when the database files reside on a filesystem or storage layer (such as ReFS or certain SAN/virtualization snapshot technologies) that fails to maintain proper write-ordering guarantees.

Step-by-Step Resolution Guide

Step 1: Validate Storage and I/O Subsystem Integrity

  • Run chkdsk C: /f /r (or the relevant volume) on Windows Server 2025 / Windows 11 to rule out filesystem-level corruption.
  • Check Windows Event Viewer under Windows Logs > System for Disk, ntfs, or storahci warnings around the time the error occurred.
  • If running on a VM, confirm the hypervisor’s storage controller and disk drivers are fully updated (VMware Paravirtual SCSI or Hyper-V Synthetic SCSI).

Step 2: Run DBCC CHECKDB Without Snapshot Isolation

  • Execute DBCC CHECKDB ('YourDatabaseName') WITH NO_INFOMSGS, ALL_ERRORMSGS, TABLOCK; — the TABLOCK option bypasses the internal database snapshot mechanism and uses table locks instead.
  • Monitor for the same LSN-based failure; if it does not reoccur, this confirms the snapshot creation process (not the actual data) was the root issue.

Step 3: Verify Database File Placement and Snapshot Directory Space

  • Confirm the drive hosting your database files (and tempdb, if using a custom snapshot directory) has sufficient free space, as internal snapshots use sparse files that grow dynamically.
  • Check sys.database_files and confirm no files report state_desc = 'OFFLINE' or unexpected growth failures in the SQL Server Error Log (Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG).
  • Move database files off of any third-party backup-driven snapshot or replication software temporarily to test for conflicts.

Step 4: Restore From a Known Good Backup if Corruption Persists

  • If DBCC CHECKDB with TABLOCK reports actual allocation or consistency errors (not just the 5278 snapshot issue), restore the database from the last verified clean full backup plus transaction log backups.
  • Use RESTORE VERIFYONLY FROM DISK = 'BackupPath.bak'; before restoring to confirm backup integrity first.

Step 5: Update SQL Server 2025 Cumulative Updates

  • Navigate to SQL Server Management Studio > Help > About to confirm your current build number.
  • Download and apply the latest Cumulative Update (CU) from the Microsoft Update Catalog, as LSN-handling bugs in snapshot creation are periodically patched.

Alternative or Verification Steps

  • Re-run DBCC CHECKDB during a low-activity maintenance window to confirm the error does not reoccur under reduced transactional load.
  • If the issue persists only under high concurrency, consider scheduling DBCC CHECKDB jobs during off-peak hours or isolating the instance from external storage-level snapshot tools (SAN replication, VSS-based backups) during the check.