ADSM-L

Re: Bad tape volume

1994-08-02 21:07:25
Subject: Re: Bad tape volume
From: Mitch Sako <mitch AT LSIL DOT COM>
Date: Tue, 2 Aug 1994 18:07:25 PDT
DISCLAIMER:

The following is not endorsed, recommended or sanctioned by IBM as far as
I know.  It's my own methodology, based upon my own experience and in no
way should be construed as the "correct" way to deal with this problem.

OK, now for my 2 cents:

I've encountered this dilemma a few times.  It has been caused when I ran
out of empty volumes for migration and he asks for a SCRATCH.  I had a
bug in my mount exit that sometimes caused it to go away while the mount
was still pending (since SCRTCH does not exist in our tape silo) and a
good volume gets mounted by a subsequent job that thought it could have
that drive.

Needless to say, a volume from another application or server often gets
clobbered if mounted R/W.

Query Contents often yields megabytes of useless data.  What I look for
are the affected nodes and filesystems, and that's about it.  Then, I
do the following:

  DEL VOL XXXXXX DISCARDATA=Y
  This will start up a background process and resync your catalog
    to what is really not there anymore
  Once this process is finished, I immediately startup incremental
    dumps for all servers affected

ADSM is smart enough to backup anything that is active and missing.  He
does this better than any other backup product that we have looked at.

What you lose is the following:

  Inactive versions of files that were on the deleted volume
  A recovery window that is as wide as it takes to backup all missing data

For the most part, ADSM is very good at solving the following requirement:

  What do you do if you have a bad volume in your backup repository
    AND you know about it?

ADSM, coupled with a redundant backup (UNIX dump, etc.) solves the next
    requirement quite well:

  What do you do if you have a bad volume in your backup repository
    AND you DON'T know about it?

In theory, backups are not needed because hardware never fails, software
never fails and nobody ever mistakenly deletes files.  Reality is quite
different and products such as ADSM do a fine job of making up for most
of these problems.

> I am running ADSM Rel 1 on VM.  We have a tape volume that the label
> was blown away on.  There is (or should I say was :-( ) data on the
> tape that now is not accessable.   I am not sure what steps I should
> take at this point to clean this up.  I tried doing a QUERY CONTENTS
> on the volume but after waiting a half hour I broke out.  The DSMSERV
> machine was not using any CPU or seeming to be active.  Is that
> command broke or was I not patient enough?  I guess my next step
> is to UPDATE VOLUME xxx UNAVAILABLE.  Will ADSM know that the current
> copies of files on the tape need to be recreated from each node on
> its next backup?  Is there something else I should do?  Any help
> will be much appreciated.
>
> Katherine Faella                 Bitnet:   KMF@URIACC
> Sr. Technical Programmer         Internet: KMF AT URIACC.URI DOT EDU
> University of Rhode Island
> Academic Computer Center
> 048 Tyler Hall
> Kingston, RI  02881              Phone:  (401) 792-2501
>

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