FSCTL_SET_ZERO_DATA IOCTL

Fills a specified range of a file with zeros (0). If the file is sparse or compressed, the NTFS file system may deallocate disk space in the file. This sets the range of bytes to zeros (0) without extending the file size.

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

C++
BOOL 
WINAPI 
DeviceIoControl( (HANDLE) hDevice,              // handle to a file
                 FSCTL_SET_ZERO_DATA,           // dwIoControlCode(LPVOID) lpInBuffer,           // input buffer
                 (DWORD) nInBufferSize,         // size of input buffer
                 NULL,                          // lpOutBuffer0,                             // nOutBufferSize(LPDWORD) lpBytesReturned,     // number of bytes returned
                 (LPOVERLAPPED) lpOverlapped ); // OVERLAPPED structure

Major Code

IRP_MJ_DEVICE_CONTROL

Input Buffer

Input Buffer Length

Output Buffer

Output Buffer Length

Input / Output Buffer

Input / Output Buffer Length

Status Block

Irp->IoStatus.Status is set to STATUS_SUCCESS if the request is successful.

Otherwise, Status to the appropriate error condition as a NTSTATUS code.

For more information, see NTSTATUS Values.

Remarks

For the implications of overlapped I/O on this operation, see the Remarks section of the DeviceIoControl topic.

If you use the WriteFile function to write zeros (0) to a sparse file, the file system allocates disk space for the data that you are writing. If you use the FSCTL_SET_ZERO_DATA control code to write zeros (0) to a sparse file and the zero (0) region is large enough, the file system may not allocate disk space.

If you use the FSCTL_SET_ZERO_DATA control code to write zeros (0) to a non-sparse file, zeros (0) are written to the file. The system allocates disk storage for all of the zero (0) range, which is equivalent to using the WriteFile function to write zeros (0) to a file.

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

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

Technology Supported
Server Message Block (SMB) 3.0 protocol Yes
SMB 3.0 Transparent Failover (TFO) Yes
SMB 3.0 with Scale-out File Shares (SO) Yes
Cluster Shared Volume File System (CsvFS) Yes
Resilient File System (ReFS) Yes

Requirements

   
Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Header winioctl.h (include Windows.h)

See Also

DeviceIoControl

FILE_ZERO_DATA_INFORMATION

FSCTL_QUERY_ALLOCATED_RANGES

FSCTL_SET_SPARSE

File Management Control Codes

Sparse Files