What does HRESULT 0xC0380042 (ERROR_VOLMGR_TOO_MANY_NOTIFICATION_REQUESTS) mean?

ERROR_VOLMGR_TOO_MANY_NOTIFICATION_REQUESTS

Why this is narrower than a generic disk error: volmgr too many notification requests

ERROR_VOLMGR_TOO_MANY_NOTIFICATION_REQUESTS has unsigned value 0xC0380042. In the volmgr layer, the operation is rejected because a notification wait is already pending for the registration and another asynchronous wait would duplicate it. Diagnosis of this result should follow volume-manager notification registration and pending wait request through one controlled state transition.

Diagnosis of this result should begin with the object model and generation current at the failure. A later successful enumeration may describe a replacement object and cannot retroactively validate the rejected request.

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 registration ID, task number, pending IRP count, process lifetime, pack ID and the notification generation returned before the failure while every handle is still valid.
3. Repeat the operation using this controlled change: register one consumer, issue exactly one asynchronous wait, complete or cancel it, and compare registration/task identifiers at each step.
4. Close and reacquire the relevant objects, then run once more to test lifecycle correctness after this result.

The distinction from ERROR_VOLMGR_MAXIMUM_REGISTERED_USERS is operational. A notification wait is already pending for the registration and another asynchronous wait would duplicate it; log the neighboring code separately so capability, identity and state are not conflated.

Mechanism-specific note

Notification registrations have two lifetimes: the registration itself and any outstanding asynchronous wait. Log both identifiers and the cancellation path. A service restart, handle close or notification reset can invalidate the old generation even when the numeric task value is later reused, so never match completion by task number alone.

Corrective action and regression check

Repair notification ownership and sequencing: cancel stale waits, unregister only live IDs, then create one replacement registration after the previous generation is closed. After correcting it, reopen the pack, volume, tier, snapshot or virtual disk so no cached generation participates in the validation run.

• 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_VOLMGR_MAXIMUM_REGISTERED_USERS and has no unbounded retry loop.

Technical references

• Microsoft: COM error codes for VOLMGR, VHD and SDIAG — documents the supported management path relevant to this HRESULT.
• Microsoft: Virtual Disk Service object model — defines the volmgr objects used to interpret it.
• Microsoft: Pack object — primary API or object-model reference.
• Microsoft: Virtual Disk Service common return codes — use this source to verify volmgr state and parameters.