Notifies a server that a client application is ready to close a file. Use this operation after notification that an opportunistic lock on a file is ready to be broken.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,                // handle to file
  FSCTL_OPBATCH_ACK_CLOSE_PENDING, // dwIoControlCodeNULL,                            // lpInBuffer0,                               // nInBufferSizeNULL,                            // lpOutBuffer0,                               // nOutBufferSize(LPDWORD) lpBytesReturned,       // number of bytes returned
  (LPOVERLAPPED) lpOverlapped      // OVERLAPPED structure

Major code


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.


Before you call this function do not make assumptions about the number of available virtual channels, because the system and other plug-ins might have reserved virtual channels. Always check for a CHANNEL_RC_TOO_MANY_CHANNELS return code after calling this function.

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

Use the FSCTL_OPBATCH_ACK_CLOSE_PENDING control code when you are notified that an opportunistic lock on a file is ready to be broken, and you intend to close the file soon. This operation does not request a new opportunistic lock.

If you do not intend to close a file, you can use the FSCTL_OPLOCK_BREAK_ACKNOWLEDGE or FSCTL_OPLOCK_BREAK_ACK_NO_2 control code to respond to the notification. The former, used if the lock being broken is an exclusive opportunistic lock, indicates the file should receive a level 2 opportunistic lock instead. The latter requests the file be kept open but loses all locking.

Applications are notified that an opportunistic lock is broken by using the hEvent member of the OVERLAPPED structure that is associated with a file on which an opportunistic lock is broken. Applications can also use functions such as GetOverlappedResult and HasOverlappedIoCompleted.

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

Technology Supported
Server Message Block (SMB) 3.0 protocol No
SMB 3.0 Transparent Failover (TFO) No
SMB 3.0 with Scale-out File Shares (SO) No
Cluster Shared Volume File System (CsvFS) Yes
Resilient File System (ReFS) Yes


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








Opportunistic Locks