Represents an update sequence number (USN) change journal, its records, and its capacity. This structure is the output buffer for the FSCTL_QUERY_USN_JOURNAL control code.


typedef struct {
  USN       FirstUsn;
  USN       NextUsn;
  USN       LowestValidUsn;
  USN       MaxUsn;
  DWORDLONG MaximumSize;
  DWORDLONG AllocationDelta;
  WORD      MinSupportedMajorVersion;
  WORD      MaxSupportedMajorVersion;


  • UsnJournalID
    The current journal identifier. A journal is assigned a new identifier on creation and can be stamped with a new identifier in the course of its existence. The NTFS file system uses this identifier for an integrity check.

  • FirstUsn
    The number of first record that can be read from the journal.

  • NextUsn
    The number of next record to be written to the journal.

  • LowestValidUsn
    The first record that was written into the journal for this journal instance. Enumerating the files or directories on a volume can return a USN lower than this value (in other words, a FirstUsn member value less than the LowestValidUsn member value). If it does, the journal has been stamped with a new identifier since the last USN was written. In this case, LowestValidUsn may indicate a discontinuity in the journal, in which changes to some or all files or directories on the volume may have occurred that are not recorded in the change journal.

  • MaxUsn
    The largest USN that the change journal supports. An administrator must delete the change journal as the value of NextUsn approaches this value.

  • MaximumSize
    The target maximum size for the change journal, in bytes. The change journal can grow larger than this value, but it is then truncated at the next NTFS file system checkpoint to less than this value.

  • AllocationDelta
    The number of bytes of disk memory added to the end and removed from the beginning of the change journal each time memory is allocated or deallocated. In other words, allocation and deallocation take place in units of this size. An integer multiple of a cluster size is a reasonable value for this member.

  • MinSupportedMajorVersion
    Indicates the minimum supported version of the USN change journal supported by the filesystem.

  • MaxSupportedMajorVersion
    Indicates the maximum supported version of the USN change journal supported by the filesystem.


Minimum supported client

Windows 8 [desktop apps only]

Minimum supported server

Windows Server 2012 [desktop apps only]


WinIoCtl.h (include Windows.h)

See also

Volume Management Structures