The access time for a file is an additional attribute where the file system will record the time and date of any read operation on the file. It is by default OFF.  You can turn it on if you need this feature and this feature is REQUIRED for data analytics software like the Scale Logic Business Intelligence (BI) so that it can show stale data that hasn't been read by anyone.  The setting is per data set.  You can turn this on during dataset creation or turn it on after creation however it will only start to record the read access time after you turn it on.