Editing MAC times (section)

== Access time (atime) ==

A file's access time identifies when the file was most recently opened for reading. Access times are usually updated even if only a small portion of a large file is examined. A running program can maintain a file as "open" for some time, so the time at which a file was opened may differ from the time data was most recently read from the file.

Because some computer configurations are much faster at reading data than at writing it, updating access times after every read operation can be very expensive. Some systems mitigate this cost by storing access times at a coarser granularity than other times; by rounding access times only to the nearest hour or day, a file which is read repeatedly in a short time frame will only need its access time updated once.<ref>
  {{cite web
    | url = http://msdn.microsoft.com/en-us/library/ms724290.aspx
    | title = File Times
    | publisher = Microsoft MSDN Library
  }}
</ref> In Windows, this is addressed by waiting for up to an hour to flush updated access dates to the disk.<ref>
  {{cite web
    | url = https://msdn.microsoft.com/en-us/library/ms724290.aspx
    | title = File Times
    | publisher = Microsoft MSDN Library
  }}
</ref>

Some systems also provide options to disable access time updating altogether. In [[Windows]], starting with [[Windows Vista|Vista]], file access time updating is disabled by default.<ref>
  {{cite web
    | url = http://blogs.technet.com/b/filecab/archive/2006/11/07/disabling-last-access-time-in-windows-vista-to-improve-ntfs-performance.aspx
    | title = Disabling Last Access Time in Windows Vista to improve NTFS performance
    | publisher = The Storage Team at Microsoft 
  }}
</ref>