ADSM-L

Re: Incremental Backup (full/partial)

2002-08-10 23:25:19
Subject: Re: Incremental Backup (full/partial)
From: "Mark D. Rodriguez" <mark AT MDRCONSULT DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Fri, 9 Aug 2002 23:02:47 -0500
KEN HORACEK wrote:

Hi fellow listers,

So here I am, "Reading the Fine Manual", and it sez; an Incremental Backup can either be 
"full" or "partial"..
How can I tell if my backup(s) are requesting a "full" or "partial" backup?

Ken
khoracek AT incsystem DOT com


Hi Everyone,

I am going to take a stab at this one.  I have seen several others have
as well.  I do want to qualify my answer and say that when I here people
refer to "full" or "partial" incremental then I give the explanation you
will see below.  I believe my explanation to be correct based on all of
my reading of the documentation as well as the education material that
IBM/Tivoli has been putting out for the last many(I think ed classes
have been around for almost 10) years.  Anyway, I certainly hope I am
right since this is the way I have been teaching it for many years.

A "full" incremental is when you issue an incremental command (command
line or scheduled) that either has no filespecs or the filespec is an
exact string of a filespace.  The following are all considered "full"
incremental:

tsm> i
tsm> i c:
tsm> i c:    d:

or on a unix box

tsm> i
tsm> i /home
tsm> i /home    /opt

This assumes that c:, d:, /home, /opt are all filespaces.

A "partial" incremental is when you qualify the backup using a filespec
that is not just a filespace name.  The following are all considered
"partial" incremental:

tsm> i c:\mydir\*
tsm> i c:\mydir\*    d:\tmp\file

or on a unix box

tsm> i /home/*
tsm> i /home    /opt

Both of these commands still process the include/exclude list in the
same way.  However, for the partial it will only backup the files based
on the filespec, i.e. some include statements will not apply.  The real
big difference between the two is that the "full" incremental will
update the value "Last Incr Date" (LID) that you see for the filespace
when you do a "q filespace".  This is a very important date a couple of
things key off of this date.  One it is used when the "-incrbydate"
option is specified(more on that later) and it is also used when your
are doing a Point In Time(PIT) restore.  All PIT restores a relative to
the previous LID, i.e. if the LID is 8/8/02 4:00 and you do a PIT
restore specifying a pitdate and pittime of 8/8/02 8:00 it will roll
back to the previous LID of 8/8/02 4:00.

The next item there seems to be a great deal of confusion about what the
"-incrbydate" option really does.  Please refer to my post on 8/8/02,
the  subject was "incremental and incremental -incrbydate" .  There was
one response that gave a completely erroneous answer, but I hope my
answer will clarify the differences between "incremental and incremental
-incrbydate".  I won't reiterate everything that I covered in that post,
but I do want to speak to what some of the people posted in this
thread.  There were a couple of post that implied that a "incremental
-incrbydate" was in fact a partial backup.  I think that is somewhat
correct but misleading.  A partial backup is as I stated above, however
what my references above and an "incremental -incrbydate" have in common
is that neither will update the LID.  The differences between the two
are much greater, remember the "-incrbydate" option changes the way
incremental decides what files will be backed up, it only compares the
files data modified time stamp to the LID and if newer back it up.  But
more significant is what it does not do:

   * Will not recognize any deleted files, i.e. no files expire.
   * Will not rebind any files if management classes have changed.
   * Ignores the copygroups frequency settings.

A "partial" incremental does effectively all the same processing as a
"full" it just does it to a subset of the files in a filespace as
defined by the filespec when the command was issued.

BTW, for those of you who pull a lot of info directly from the TSM DB,
the LID can be found in the table "filespaces" and the attribute is
"BACKUP_END", as you can see it is actual the time stamp of when the
"full" incremental has completed.

I apologize for such a long post, I just hate to see confusion about
important concepts that TSM is based upon.  I good understanding of the
basic concepts and terminology goes a long way.


--
Regards,
Mark D. Rodriguez
President MDR Consulting, Inc.

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