Frank,
        Yes, you need to look at this in a different perspective.  For backups,
ADSM uses version control (keep _n_ copies of a file if it's active
regardless of how old it is - active = exists on the client as of the
last backup) and a combination of version and retention period control
for inactive files (files no longer on the server as of the last ADSM
incremental backup).  If you're at all familiar with SMS on MVS, it's
very similar to the way an SMS Management Class works (backup frequency
/ # backups ds exists / # backups ds deleted / retain days only backup /
retain days extra backup).  Over time, as files expire and tapes become
partially full, these tapes are merged as part of reclamation
processing.  One factor to consider in setting up your ADSM environment
is whether or not to enable collocation  Enabling collocation tells ADSM
to keep each client's data on separate tapes.  With collocation
disabled, ADSM tries to fill each tape before writing to a new tape.
The upside to using collocation is that each client's data is on a
separate set of tapes which can speed up restores significantly. The
downside to collocation - more tapes are used, more tape mounts, more
background processing (tape reclamation).  Things to keep in mind when
deciding this are client size, tape capacity, etc.  Also, you can use
collocation for some clients and not for others by setting up separate
storagepools.
        This type of incremental backup philosophy takes some getting used to
as it differs radically from traditional backup methodologies.  I can
tell you from experience that we've used ADSM to do more than a few full
client (Netware, OS/2, NT, etc.) recoveries and full file system
recoveries (AIX, HPUX, Ultrix) over the past 2.5 years and it hasn't
failed us yet.

Tim Pittson
tpittson AT himail.hcc DOT com

>----------
>From:  Frank Rehor[SMTP:Frank.Rehor AT CLOROX DOT COM]
>Sent:  Thursday, May 23, 1996 8:10 PM
>To:    Multiple recipients of list ADSM-L
>Subject:       Incremental vs Full Backups
>
>We are in the process of implementing ADSM for the first time in our
>shop
>and I'm trying to clear up some confusion on our part re: backups.  We
>come from a mainframe environment where we do weekly 'full' backups of
>datasets (backup all files in the shop) and daily 'incrementals'
>(backup
>only files changed since the last backup).  If we need to recover our
>system we restore the latest backup of a dataset which is, at most,
>only a
>week old.
>
>In ADSM we see only incremental backups.  Granted the first backup is
>truly
>a 'Full' since nothing has been backed up prior.  If a file does not
>get
>updated periodically it won't be backed up again.  The concern is how
>long
>we must keep backups to guarantee there being an available means to
>recover
>a file that, e.g., may be read only or updated very infrequently.
>
>Any feedback would be helpful.  Do we need to look at this from a
>totally
>different perspective than the mainframe world?
>