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ERROR_NOTIFICATION_GUID_ALREADY_DEFINED
The file already has a notification identifier
ERROR_NOTIFICATION_GUID_ALREADY_DEFINED is a Win32 result associated with filesystem notification metadata., diagnosis should begin with the exact API, target object, and operation that produced it rather than with the message text alone.
What the result means
A notification GUID is already associated with the specified file. The practical meaning depends on the caller and on whether the affected object is local, remote, removable, policy-managed, or handled asynchronously. Diagnostics for it should retain its symbolic name, numeric value, and the operation name together.
What to check
- Query the existing identifier before attempting to assign another.
- Determine whether the operation is being repeated idempotently or by competing components.
- Use the existing GUID when it belongs to the same logical registration.
- Coordinate ownership when multiple services manage the same file.
Recommended handling
Do not overwrite an existing identifier blindly. Conflicting notification identities can cause duplicate, missed, or misrouted events.
Developer notes
Code handling this result should capture the failing API, resolved path or device identity, requested access, process identity, and the first observed error. After a call that reports it, read GetLastError() immediately because later cleanup or logging can overwrite the value. Retry it only when the specific condition is documented as transient, using a bounded delay and cancellation support.
References
- Microsoft: System error codes relevant to ERROR_NOTIFICATION_GUID_ALREADY_DEFINED
- Microsoft: File management context for ERROR_NOTIFICATION_GUID_ALREADY_DEFINED
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