Enables or disables the mechanism that ejects media. Disabling the mechanism locks the drive.

To perform this operation, call the DeviceIoControl function with the following parameters.

BOOL DeviceIoControl(
  (HANDLE) hDevice,                // handle to device
  (LPVOID) lpInBuffer,             // input buffer
  (DWORD) nInBufferSize,           // size of input buffer
  NULL,                            // lpOutBuffer
  0,                               // nOutBufferSize
  (LPDWORD) lpBytesReturned,       // number of bytes returned
  (LPOVERLAPPED) lpOverlapped      // OVERLAPPED structure



A handle to the device. To obtain a device handle, call the CreateFile function.

Files must be opened with the FILE_READ_ATTRIBUTES access right. For more information, see File Security and Access Rights.


The control code for the operation. Use IOCTL_STORAGE_EJECTION_CONTROL for this operation.


A pointer to a PREVENT_MEDIA_REMOVAL structure.

If the PreventMediaRemoval member is TRUE, the media cannot be ejected (the device is locked). Otherwise, the media can be ejected (the device is unlocked).


The size of the input buffer, in bytes.


Not used with this operation; set to NULL.


Not used with this operation; set to zero.


A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.

If lpOverlapped is NULL, lpBytesReturned cannot be NULL. Even when an operation returns no output data and lpOutBuffer is NULL, DeviceIoControl makes use of lpBytesReturned. After such an operation, the value of lpBytesReturned is meaningless.

If lpOverlapped is not NULL, lpBytesReturned can be NULL. If this parameter is not NULL and the operation returns data, lpBytesReturned is meaningless until the overlapped operation has completed. To retrieve the number of bytes returned, call GetOverlappedResult. If hDevice is associated with an I/O completion port, you can retrieve the number of bytes returned by calling GetQueuedCompletionStatus.


A pointer to an OVERLAPPED structure.

If hDevice was opened without specifying FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. In this case, lpOverlapped must point to a valid OVERLAPPED structure that contains a handle to an event object. Otherwise, the function fails in unpredictable ways.

For overlapped operations, DeviceIoControl returns immediately, and the event object is signaled when the operation has been completed. Otherwise, the function does not return until the operation has been completed or an error occurs.

Return value

If the operation completes successfully, DeviceIoControl returns a nonzero value.

If the operation fails or is pending, DeviceIoControl returns zero. To get extended error information, call GetLastError.


The driver tracks IOCTL_STORAGE_EJECTION_CONTROL requests by caller. It ignores requests to enable the ejection mechanism unless it has received a request to disable the ejection mechanism from the same caller. This prevents other callers from unlocking the drive.


Minimum supported client

Windows XP

Minimum supported server

Windows Server 2003


WinIoCtl.h (include Windows.h)

See also

Device Management Control Codes