FSCTL_RECALL_FILE control code

Applies to: desktop apps only

Recalls a file from storage media that Remote Storage manages, which is the hierarchical storage management software.

To recall a file, call the DeviceIoControl function with the following parameters.

BOOL DeviceIoControl(
  (HANDLE) hDevice,            // handle to file or directory
  FSCTL_RECALL_FILE,           // dwIoControlCode
  NULL,                        // lpInBuffer
  0,                           // nInBufferSize
  NULL,                        // lpOutBuffer
  0,                           // nOutBufferSize
  (LPDWORD) lpBytesReturned,   // number of bytes returned
  (LPOVERLAPPED) lpOverlapped  // OVERLAPPED structure
);

Parameters

hDevice

A handle to the file that has data to be recalled from remote storage media.

To retrieve a device handle, call the CreateFile function. The handle must be opened with read access, write access, or both. For more information, see File Security and Access Rights.

dwIoControlCode

The control code for the operation.

Use FSCTL_RECALL_FILE for this operation.

lpInBuffer

Not used with this operation; set to NULL.

nInBufferSize

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

lpOutBuffer

Not used with this operation; set to NULL.

nOutBufferSize

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

lpBytesReturned

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

If lpOverlapped is NULL, lpBytesReturned cannot be NULL. Even when an operation does not return output data and lpOutBuffer is NULL, DeviceIoControl uses lpBytesReturned. After that kind of 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 is complete. 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.

lpOverlapped

A pointer to an OVERLAPPED structure.

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

If hDevice is opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. In this scenario, 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 is complete. Otherwise, the function does not return until the operation is complete 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 0 (zero). To get extended error information, call GetLastError.

Remarks

FSCTL_RECALL_FILE recovers a file from storage, for example, a tape that is managed by Remote Storage. If the file is already cached locally, this operation does nothing. Similarly, if the file has not been moved to remote storage, this operation does nothing.

FSCTL_RECALL_FILE operates only on systems where Remote Storage is installed. If Remote Storage is not installed, the operation fails and GetLastError returns the error code ERROR_INVALID_FUNCTION.

Directories cannot be moved to remote storage. Calling FSCTL_RECALL_FILE for a directory fails, and GetLastError returns the error code ERROR_INVALID_HANDLE.

Typically, files that are stored on media that is managed by Remote Storage are recalled when an application attempts to make the first access to data. An application that opens a file without immediately accessing the data can speed up the first access by using FSCTL_RECALL_FILE immediately after opening the file. However, avoid indiscriminate recall of files that an application does not touch.

Before you call FSCTL_RECALL_FILE you do not need to test a file's attributes for the flag FILE_ATTRIBUTE_OFFLINE with the function GetFileAttributes. The test is unnecessary because an online file is not affected by this operation. However, any operating system call takes processor time. To conserve processor time, call GetFileAttributes to check file attributes to determine if FSCTL_RECALL_FILE is necessary.

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

Examples

The following code example is a command-line utility that recalls one or more files indicated on the command line from remote storage.

#include <Windows.h>
#include <malloc.h>
#include <stdio.h>
#include <WinIoCtl.h>

DWORD RecallFile(PTCHAR FileName);

int _cdecl _tmain(int argc, TCHAR *argv[])
{
  LONG i;

  if (argc < 2) {
    printf("Usage: recall <file-name1> <file-name2> ...\n");
    return 1;
  }

  for (i = 1; i < argc; i++) {
    (void) RecallFile((PTCHAR) argv[i]);
  }
  return 0;
}

DWORD RecallFile(IN PTCHAR FileName)
  /*++
Routine Description
    Recalls the file with the supplied path.
Arguments
    FileName - Path of the file to be recalled
Return Value
    0                   - Recall is successful.
    Any other value     - Error code for the operation.

--*/

{
  HANDLE fileHandle;
  DWORD  nbytes;
  DWORD  errorCode = 0;

  fileHandle = CreateFile((LPCTSTR) FileName,
                          GENERIC_READ,
                          FILE_SHARE_READ,
                          NULL,
                          OPEN_EXISTING,
                          FILE_ATTRIBUTE_NORMAL,
                          NULL);

  if (fileHandle == INVALID_HANDLE_VALUE) 
  {
    errorCode = GetLastError();
    printf("Couldn't open file %s: error %x\n", FileName, 
           errorCode);
    return errorCode;
  }

  if (!DeviceIoControl(fileHandle,
                       FSCTL_RECALL_FILE,
                       NULL,
                       0,
                       NULL,
                       0,
                       &nbytes,
                       NULL)) 
  {
    errorCode = GetLastError();
    printf("Couldn't recall file %s: error %x\n", 
           FileName, errorCode);
  }
  CloseHandle(fileHandle);
  return errorCode;
}

Requirements

See also

CreateFile

DeviceIoControl

File Management Control Codes

GetFileAttributes

OVERLAPPED

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Build date: 4/17/2012