What does HRESULT 0xC03A001F (ERROR_VIRTDISK_DISK_ONLINE_AND_WRITABLE) mean?

ERROR_VIRTDISK_DISK_ONLINE_AND_WRITABLE

Why this is narrower than a generic disk error: virtdisk disk online and writable

Windows returns ERROR_VIRTDISK_DISK_ONLINE_AND_WRITABLE, value 0xC03A001F, at the virtdisk boundary. It means that the physical disk is online with write access when the operation requires it to be offline or read-only. Preserve the exact handle and generation of Virtual Disk API provider, image format and host-disk state before any rescan changes the evidence.

The Virtual Disk API chooses a format provider from VIRTUAL_STORAGE_TYPE, opens an image with explicit access rights and can attach it as a disk. Provider selection, backing-chain integrity, host-file attributes, sector geometry and operating-system ownership are independent validation stages.

Storage facts that change the diagnosis

When it is followed by a secondary cleanup failure, store both codes with timestamps and retain this one as the initiating result.

A/B test

1. serialize the failing request and the enumeration from which its identifiers came.
2. Preserve image path, VIRTUAL_STORAGE_TYPE, provider/vendor IDs, VHD/VHDX/VHD Set identifiers, host sector sizes, attach flags, ownership and online/read-only state while every handle is still valid.
3. Repeat the operation using this controlled change: record the current owner and disk attributes, release or offline the disk in a test scope, and retry without changing the image.
4. Close and reacquire the relevant objects, then run once more to test lifecycle correctness after this result.

ERROR_VIRTDISK_DISK_ALREADY_OWNED describes a nearby but different storage condition; this result indicates that the physical disk is online with write access when the operation requires it to be offline or read-only.

Mechanism-specific note

The physical disk attributes are incompatible with an operation that needs exclusive offline or read-only access. Capture disk number, unique ID and current attributes. Offline the correct disk only after proving it is not serving a mounted volume, cluster resource or another virtual machine.

Corrective action and regression check

Correct the provider, image format, backing-file chain, host geometry or disk ownership identified by the failing call, then reopen the image to obtain a new handle before retrying. Apply the change through the supported storage API, then close and reacquire affected objects before retrying.

• The original request now reaches success or a documented later status with the intended layout and access mode.
• A new enumeration reports internally consistent IDs, counts, geometry and ownership for the corrected object.
• The passing state survives the relevant lifecycle transition, such as reopen, remount, owner change or detach/attach.
• The application still distinguishes it from ERROR_VIRTDISK_DISK_ALREADY_OWNED and has no unbounded retry loop.

Technical references

• Microsoft: Virtual Disk API — primary API or object-model reference.
• Microsoft: OpenVirtualDisk — use this source to verify virtdisk state and parameters.
• Microsoft: AttachVirtualDisk — documents the supported management path relevant to this HRESULT.
• Microsoft: GetVirtualDiskInformation — defines the virtdisk objects used to interpret it.