What is Error 9555?
Windows System Error Code 9555, known as DNS_ERROR_NOT_UNIQUE, is a Cluster & Storage error that occurs during cluster, backup, and storage management. The error indicates that: Record for given name and type is not unique. When this error is encountered, the Windows operating system was unable to complete the requested operation within the storage/cluster services subsystem. The error code 9555 is returned by the GetLastError() function and provides developers with a specific identifier to diagnose the root cause of the failure. The symbolic name DNS_ERROR_NOT_UNIQUE maps directly to this numeric code and is commonly referenced in Microsoft documentation, developer forums, and system logs. Understanding this error and its context within cluster, backup, and storage management is essential for effective troubleshooting.
Common Causes
- System resource conflict: Record for given name and type is not unique.
- Quorum lost due to node failure
- Storage paths disconnected
- Cluster service dependency failure
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Read the full guide →Step-by-Step Solutions
- Open PowerShell as Administrator
- Run: Get-ClusterNode to check node status
- Run: Test-Cluster for full validation
- Review the HTML report for issues
Video Tutorials
Diagnostic Command
Run this PowerShell command to find related events in your system log:
Get-EventLog -LogName System -Newest 20 | Where-Object {$_.Message -like "*9555*" -or $_.Message -like "*DNS_ERROR_NOT_UNIQUE*"} | Format-List💡 Open PowerShell as Administrator, paste the command above, and press Enter.
Prevention Tips
- Configure redundant storage paths (MPIO)
- Validate cluster after updates
- Monitor disk latency and capacity