starting in version 6.0, "shadow paging" was used instead of pre-imaging, and it is still used to this day. instead of copying the page into a temporary file, the next spare physical location in the database file was found and the page was written to this location. this page is called a "shadow page" because it still has not had its location written to the file's pat. once the update to the shadow page completed, the pat was updated and the entry recorded in the pat of the next available and current physical page in the file. however, if a system failure occurred while doing the update to the shadow page the pat would not be updated and so the change would be dropped because the current and next entry was not updated in the pat.