FSCTL_SET_OBJECT_ID control code

Sets the object identifier for the specified file or directory.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,           // handle to device
  FSCTL_SET_OBJECT_ID,        // dwIoControlCode
  (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 file or directory whose object identifier is to be set. The process opening the file must have restore privilege, and the file must be opened with restore intent and write access. To retrieve a device handle, call the CreateFile function.


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


A pointer to the input buffer, a FILE_OBJECTID_BUFFER structure.


The size of the input buffer, in bytes.


Not used with this operation; set to NULL.


Not used with this operation; set to zero (0).


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 (0). To get extended error information, call GetLastError.


Object identifiers are used to track files and directories. They are invisible to most applications and should never be modified by applications. Modifying an object identifier can result in the loss of data from portions of a file, up to and including entire volumes of data.

Use this operation to explicitly set an object identifier to a value you provide. Attempting to set an object identifier on an object that already has an object identifier will fail. An attempt to use an object identifier that is already in use on the volume will also fail. Use the FSCTL_CREATE_OR_GET_OBJECT_ID operation to have the NTFS file system generate an object identifier if the object does not already have one.

Note that the time stamps may not be updated correctly for a remote file. To ensure consistent results, use unbuffered I/O.

In Windows 8 and Windows Server 2012, this code is supported by the following technologies.


Server Message Block (SMB) 3.0 protocol


SMB 3.0 Transparent Failover (TFO)


SMB 3.0 with Scale-out File Shares (SO)


Cluster Shared Volume File System (CsvFS)


Resilient File System (ReFS)




Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]


WinIoCtl.h (include Windows.h)

See also

Object Identifiers