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| ERROR_UNABLE_TO_UNLOAD_MEDIA | ERROR_BUS_RESET |
ERROR_MEDIA_CHANGED
the media in the drive may have changed.
ERROR_MEDIA_CHANGED means that a removable-media device indicates that the loaded medium or its generation changed since the caller established state. In this case, the decisive context is removable disks, optical drives, tape devices, and card readers, together with device and volume identity before and after the event.
Where the result appears
- removable disks, optical drives, tape devices, and card readers.
- applications caching volume geometry, labels, catalogs, or file handles.
- device reset or operator media exchange.
- virtual removable-media changes in hypervisors or remote management.
Typical causes
- the user or library replaced the medium.
- the device was reset and invalidated its change counter.
- a virtual-media provider attached a different image.
- the same physical medium was reloaded and must be revalidated.
Evidence to collect
- device and volume identity before and after the event.
- change counter, media serial/label, mount events, and handle timestamps.
- operator/library actions and virtual-media management logs.
- which cached geometry, catalog, or filesystem assumptions remain in use.
For this condition, begin the investigation with device and volume identity before and after the event. Correlate it with change counter, media serial/label, mount events, and handle timestamps and check whether the user or library replaced the medium. Capture the original this result immediately after the failing call so later cleanup does not replace the thread-local error value.
Handling and recovery
Invalidate cached media-dependent state, close stale handles, re-query the device, and verify identity before continuing. For writes, require explicit confirmation that the newly detected medium is the intended target.
Any retry policy for this Win32 error should be tied to evidence that the device was reset and invalidated its change counter has changed. Before another attempt, verify operator/library actions and virtual-media management logs. If the same physical medium was reloaded and must be revalidated still applies, stop the retry sequence and preserve the first diagnostic event.
Common misinterpretation
The wording says “may have changed” because the driver detects a generation transition, not necessarily a confirmed human swap. Revalidation is still required.
Guidance for developers
When surfacing this result through another layer, retain its Win32 domain, numeric value, and the operation described by applications caching volume geometry, labels, catalogs, or file handles. A useful telemetry record also includes which cached geometry, catalog, or filesystem assumptions remain in use. For a-related handling, decisions must use the numeric value and documented API contract rather than localized wording.
A focused test should reproduce the condition in which a virtual-media provider attached a different image, assert this result, and confirm that the program releases resources associated with device reset or operator media exchange. The recovery test should also verify that device and volume identity before and after the event is refreshed before the operation resumes.
References
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