What’s the issue?
SQL Server records every backup attempt in the SQL Server error log, including both successful backups and any that fail with an error. Failed backup entries include the database name, the type of backup attempted, the destination, and the specific error that caused the failure, providing a useful diagnostic record for backup-related issues.This finding identifies instances where the error log contains entries for one or more recent failed backups. The detection is based on scanning the error log for backup-related error messages, typically those generated by failed BACKUP DATABASE or BACKUP LOG commands.
A failed backup can result from many causes, including disk space exhaustion on the backup target, network connectivity problems to remote backup locations, permissions issues on the destination, corruption in the source database, conflicts with other backup processes, or specific configuration problems such as expired backup encryption certificates.
Why is this a problem?
A failed backup is a gap in the recovery chain. Whether the failed backup is a full, differential, or transaction log backup, its absence affects what can be recovered and how far back recovery is possible. Repeated log backup failures are particularly serious in databases using the FULL recovery model, since they can cause the transaction log to grow continuously and prevent point-in-time recovery for the affected window.Backup failures often go unnoticed when monitoring is not specifically configured to alert on them. The SQL Server Agent job that runs the backup may continue to run on schedule, and the next attempt may succeed, leaving the failure visible only in the error log and the job history. Reviews that focus on whether backups are running rather than whether they are succeeding can miss the gap entirely.
The condition is also a useful signal for broader infrastructure issues. Backup destinations are often shared across many databases or instances, and a failure on one backup can indicate a problem (full disk, failing storage, network outage) that affects others as well. Investigating a failed backup early can prevent a larger disruption.
Failed backup entries in the error log also produce noise during other troubleshooting. When a backup fails repeatedly, the error log fills with backup error messages that can obscure other issues, making it harder to find unrelated entries when investigating different problems.
What should you do about this?
Address the underlying cause based on the specific error. Common remediations include freeing disk space on the backup target, restoring network connectivity to the backup location, correcting permissions for the SQL Server service account on the destination, resolving conflicts with overlapping backup jobs, or replacing an expired backup encryption certificate (covered in a separate finding).Once the root cause is fixed, run a successful backup of each affected database to reestablish the recovery chain. For databases in the FULL recovery model where log backups have been failing, take a fresh log backup as soon as the issue is resolved, and check that the transaction log file is truncating normally afterward. If log space has grown excessively while backups were failing, plan log file management as a follow-up activity.
Also, investigate why the backup failure was not detected and addressed promptly. If monitoring is not catching failed backups, configure alerts on backup job failures, on the absence of recent successful backups for each database, and on conditions such as transaction log growth that can result from sustained backup problems. The goal is to detect and address backup failures within the same day rather than discovering them after they have produced larger consequences.