ADSM-L

Why is the same tape mounted several times during a restore?

1997-11-20 05:35:39
Subject: Why is the same tape mounted several times during a restore?
From: Larry Robertson <Larry_Robertson AT COMPUWARE DOT COM>
Date: Thu, 20 Nov 1997 05:35:39 EST
I just performed a restore for a client that deleted a marketing directory that
had 84 sub-directories beneath it. There were a total of about 1200 files (2
GB). Unfortunately they did not tell me until after the next incremental was run
so that all of the deleted directories and files were marked inactive. I used a
line command to restore the data and learned first hand the value of Version 3's
point-in-time restore when ADSM also restored all of the files that the client
had deleted over the past 60 days. (approximately 800 files, 1 GB)
restore d:\inet\www\marketing\* -subdir=yes -latest
I do not use collocation so the data for the client was spread across 38
volumes. If this wasn't bad enough it mounted 17 of the tapes twice for a total
of 55 mounts. Why isn't ADSM smart enough to restore all of the files needed
from each tape the first time it's mounted? It looks like ADSM called for the
tapes in volume sequence except in the case of the re-mounted volumes:
AB0005
AB0009
AB0013
AB0009   <- Second mount
AB0013   <- Second mount
AB0029
Etc.

If this wasn't already enough fun, during my first attempt to do the restore
after about 40 tapes the session timed out because it was waiting for a reply
that I failed to answer quick enough. (15 minute default).

So I started the restore again thinking that it would pick up where it left off.
restore d:\inet\www\marketing\* -subdir=yes -latest -replace=no
I was surprised and disappointed that ADSM called for all of the same tapes
again, all forty before it got to the point where it began restoring data again.
During the first forty tapes it gave be a "Skipping" message for all of the
files that it restore during the first attempt.
When ADSM builds the list of files that need to be restored, why does it try to
restore the files that already exist? With -replace=no couldn't it compare the
list of files that the database knows about to the hard drive and determine that
there is no need to mount the tape and attempt the restore?

I plan on ordering Version 3 for AIX this week. Hopefully my restores will go
smoother in the future.

Larry Robertson
Compuware Corporation
larry_robertson AT compuware DOT com
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