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ERROR_LOST_WRITEBEHIND_DATA_NETWORK_SERVER_ERROR
delayed-write data was lost because the remote server returned an error.
ERROR_LOST_WRITEBEHIND_DATA_NETWORK_SERVER_ERROR means that this condition The client remained able to communicate, but the server rejected or failed a write that Windows had queued. Server-side storage exhaustion, quotas, failover, permissions, file-system errors, or an SMB implementation failure can all produce this distinction.
Where the result appears
- remote writes that fail after buffering on the Windows client.
- clustered file-server failover or storage outage.
- NAS devices returning an error during cache flush.
- applications closing a remote file after a server-side allocation failure.
What the result tells you
The value identifies a specific Windows state, but it does not by itself identify the component that introduced that state. Preserve the original this result value, the API or subsystem that produced it, and the object being operated on. A wrapper that replaces it with a generic exception or Boolean failure removes the distinction needed to choose the correct recovery path.
Diagnostic evidence to collect
- the server-reported SMB status and any translated Win32 code.
- server disk capacity, quota, file-system, and cluster events.
- the remote path, share configuration, and durable-handle state.
- file length and checksum on both client expectation and server reality.
Correlate the result evidence on one timeline. The first event that changes the state associated with this result is usually more valuable than later retries returning the same code. Record process and thread identity, session, timestamp, API parameters, and the immediately preceding successful operation.
Handling and recovery
Investigate the server before retrying. Free capacity or fix the server-side fault, then recreate or verify the entire affected file. For transactional outputs, write to a temporary name, flush, validate, and rename only after the server confirms durability.
Retry after this result only when the evidence shows that an external condition can change. When it is caused by malformed input, revoked authority, unsupported state, hardware damage, or an offline maintenance requirement, an unchanged retry adds noise and can overwrite the earliest useful diagnostics.
Common misinterpretation
This variant is not primarily a cable or Wi-Fi problem. The network delivered the request far enough for the server to return an error.
Guidance for developers
Keep it in its Win32/LRESULT domain in structured telemetry. When converting it to an HRESULT, exception, RPC response, or JSON field, retain the source domain and numeric value alongside the human-readable text. Do not branch on the localized message string for it.
A it test should construct the specific state, assert the exact result, and verify that partial resources are released. The recovery test for it should prove that the operation is either deferred until a measurable state change or fails without an uncontrolled retry loop.
References
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