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ERROR_UNABLE_TO_UNLOAD_MEDIA
unable to unload the media.
ERROR_UNABLE_TO_UNLOAD_MEDIA means that the device could not eject, rewind-and-unload, or otherwise remove the currently loaded medium. In this case, the decisive context is tape libraries and standalone drives, together with outstanding handles and I/O, lock state, reservation owner, and drive status.
Where the result appears
- tape libraries and standalone drives.
- optical and removable storage eject operations.
- backup job completion and media rotation.
- operator or automation requests to move media.
Typical causes
- the device is busy, reserved, or still has outstanding I/O.
- media is physically stuck or the mechanism reported a fault.
- the drive requires rewind, unlock, or another preparatory step.
- library inventory, robotics, or drive state is inconsistent.
Evidence to collect
- outstanding handles and I/O, lock state, reservation owner, and drive status.
- sense codes, firmware events, and library robotics logs.
- whether rewind completed and the medium is at a valid unload position.
- physical indicators and whether manual intervention was attempted.
For this condition, begin the investigation with outstanding handles and I/O, lock state, reservation owner, and drive status. Correlate it with sense codes, firmware events, and library robotics logs and check whether the device is busy, reserved, or still has outstanding I/O. Capture the original this result immediately after the failing call so later cleanup does not replace the thread-local error value.
Handling and recovery
Stop new I/O, close handles, complete required rewind/unlock steps, and retry only after the drive reports ready. Repeated unload commands against a mechanical fault can worsen damage. Escalate to operator intervention according to the device procedure.
Any retry policy for this Win32 error should be tied to evidence that media is physically stuck or the mechanism reported a fault has changed. Before another attempt, verify whether rewind completed and the medium is at a valid unload position. If library inventory, robotics, or drive state is inconsistent still applies, stop the retry sequence and preserve the first diagnostic event.
Common misinterpretation
Failure to unload does not prove that data on the medium is unreadable; it may be an ownership or mechanical-state problem.
Guidance for developers
When surfacing this result through another layer, retain its Win32 domain, numeric value, and the operation described by optical and removable storage eject operations. A useful telemetry record also includes physical indicators and whether manual intervention was attempted. For the-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 the drive requires rewind, unlock, or another preparatory step, assert this result, and confirm that the program releases resources associated with backup job completion and media rotation. The recovery test should also verify that outstanding handles and I/O, lock state, reservation owner, and drive status is refreshed before the operation resumes.
References
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