Path: utzoo!attcan!uunet!husc6!bbn!uwmcsd1!ig!agate!ucbvax!CITHEX.CALTECH.EDU!carl
From: carl@CITHEX.CALTECH.EDU (Carl J Lydick)
Newsgroups: comp.os.vms
Subject: RE: Uses for access time
Message-ID: <880506120409.1d20@CitHex.Caltech.Edu>
Date: 6 May 88 19:17:50 GMT
References: <8805021633.AA19865@scgvaxd.SCG.HAC.COM>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 25


 > Yes.  These are reasons enough.  Security (knowing whether a file has
 > been modified, and when) is a singular "reason enough!"  One of the other
 > important reasons for recording last-access time (most especially
 > last-modified time) is for backup purposes.  Performing an incremental
 > backup would be difficult without knowing which files had changed at what
 > times.  An operating system ~could~ just maintain a one-bit flag for each
 > file indicating 'file-modified', and reset the bit each time the file was
 > backed-up.  But this austere method eliminates security tracking and
 > precludes any flexibilty on selective backups (by date/time) {in the words
 > of Yul Bryner: etc, etc, etc...}

I'm afraid that Brian Hagerty is missing the point.  The  question  was  about
last  access  time, as distinct from last modification time.  There are, as he
states, very good reasons for maintaining  a  last  modification  time.   Last
access  time  is  less clearly useful unless you're running in a pretty secure
environment and need to know if someone has seen something he shouldn't.   The
main  use  I've  seen  for  maintaining  a  last-access time for a file is for
archiving purposes:  if nobody's used a file for a long time, you  might  want
to  move  it  to  tape.  If you've got only a few sensitive files, you can put
alarm acl's on them.  For archiving purposes, you don't  need  to  keep  close
track  of the last access time; you need a resolution equal to how long it can
be since a file has been accessed before you want to archive it.  This can  be
done  by  setting  the  retention  period  on the volume (on CITHEX, this is 6
months minimum, 6 months and a day maximum).