TROUBLESHOOTING OPERATING SYSTEM ERROR 3
When executing a database backup job, SQL Backup Master may report a failure with the following SQL Server error:
Cannot open backup device '<Path>'. Operating system error 3 (The system cannot find the path specified.)
The core issue behind this error is that SQL Server itself must be able to write backup files directly to the temporary backup folder location specified in your backup job settings. When it can't – because of permissions, an inaccessible path, or a security boundary – SQL Server raises operating system error 3 and the backup fails. The causes below are listed in order of how frequently we see them.
Cause 1 – Permissions issues
SQL Server operates under the security context of the account specified in the SQL Server system service configuration – not the account you're logged in with. If that service account can't write to the temporary backup folder, the backup fails with this error.
To verify which account SQL Server is using, and confirm its access to the folder:
- Click Start and type services.msc in the search box, then press ENTER.
- Find your SQL Server instance in the service list, double-click it, and select the Log On tab. Note the account shown there.
- Right-click the temporary backup folder in Windows Explorer.
- Select Properties, then navigate to the Security tab.
- Confirm the SQL Server service account has explicit read/write permissions on the folder. If it doesn't, add them.
Quick troubleshooting tip: temporarily grant "everyone" full permissions on the temporary backup folder. If the backup then succeeds, you've confirmed that permissions are the issue – remove the "everyone" grant and give the SQL Server service account the specific read/write permissions it needs instead.
Cause 2 – Mapped drives
Mapped drive letters are bound to the Windows security context that was used to create them,
and SQL Server will usually not be able to access the mapping. A path like
Z:\DBBackups that works fine in your Explorer session simply doesn't exist from
the SQL Server service's point of view.
Solution: use a fully qualified UNC path instead of a mapped drive letter.
For example, use \\remote-server\DBBackups instead of Z:\DBBackups.
Cause 3 – Lack of domain trust
If SQL Server and the backup folder reside in separate Active Directory domains, a missing or expired trust relationship between the domains can cause this error even when file system permissions look correct. Establish domain trust and configure the SQL Server service account with pass-through authentication between the domains.
Related resources
If you're still seeing operating system error 3 after working through the causes above, please open a support request and we'll be happy to help.