The server provides:
Open: An Open of a DataStream or DirectoryStream.
OutputBufferSize: The maximum number of bytes to return in OutputBuffer.
On completion, the object store MUST return:
Status: An NTSTATUS code that specifies the result.
BytesReturned: The number of bytes returned in OutputBuffer.
Support for this operation is optional. If the object store does not implement this functionality, the operation MUST be failed with STATUS_INVALID_DEVICE_REQUEST.<132>
Pseudocode for the operation is as follows:
If Open.File.Volume.IsReadOnly is TRUE, the operation MUST be failed with STATUS_MEDIA_WRITE_PROTECTED.
If OutputBufferSize is less than sizeof(Usn), the operation MUST be failed with STATUS_INVALID_PARAMETER.
If Open.File.Volume.IsUsnJournalActive is FALSE, the operation MUST be failed with STATUS_JOURNAL_NOT_ACTIVE.
The object store MUST post a USN change as specified in section 22.214.171.124 with File equal to File, Reason equal to USN_REASON_CLOSE, and FileName equal to Open.Link.Name.
The object store MUST populate the fields of OutputBuffer as follows:
OutputBuffer.Usn set to Open.File.Usn.
Upon successful completion of the operation, the object store MUST return:
BytesReturned set to sizeof(Usn).
Status set to STATUS_SUCCESS.