What does Windows error code 2401 (ERROR_OPEN_FILES) mean?

 
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ERROR_NOT_CONNECTED ERROR_ACTIVE_CONNECTIONS

ERROR_OPEN_FILES

The network connection still has open files or pending requests.

ERROR_OPEN_FILES is Win32 error 2401 (0x961). WNetCancelConnection2 can return it when forced disconnection is disabled and the connection still backs open files or active jobs. The status protects in-flight work from being severed; it is not evidence that the share itself is offline.

What keeps the connection busy

  • the application still owns file, directory, search, printer, or mapped-view handles on the remote resource
  • another process in the same logon session uses the mapped drive or UNC connection
  • asynchronous reads, writes, flushes, or copy operations have not completed
  • a shell window, current working directory, antivirus scanner, indexer, or backup tool references the share
  • cleanup closes the drive mapping before child workers and libraries release their network objects

Evidence before any forced disconnect

Record the local device and remote name, caller logon session, cancel flags, application-owned handle/job counts, pending I/O and worker states, processes known to use the mapping, and whether the connection is persistent. Do not log remote file contents or sensitive full paths unless required for diagnosis.

Diagnostic sequence

Stop new work, wait for application operations, close all owned handles, and ensure no thread uses the mapping as its current directory. Retry without force. If 2401 remains, use operating-system handle and SMB/session diagnostics to identify other consumers under the same context.

Determine whether the requested name is a drive letter or remote resource and whether several mappings share one server session. Closing one application object may not end all activity associated with the connection.

Recovery and user choice

Prefer graceful closure and retry. Use the force option only after warning that open data can be lost and after the owner has accepted that risk. A service should not force-disconnect a connection shared with interactive applications.

Design shutdown as quiesce, drain, close, then disconnect. Track remote resources with explicit ownership instead of assuming process termination immediately releases every network request.

Difference from active connections

ERROR_ACTIVE_CONNECTIONS can describe broader active references or dependent connections. Error 2401 specifically highlights open files or requests that make a nonforced WNet cancellation unsafe.

Example

A backup agent finishes copying but leaves a directory enumeration handle open, then tries to remove drive Z:. WNet returns 2401. Closing the enumeration and waiting for the final flush allows a normal disconnect without forcing it.

References

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