> For further confusion, I read this under "Using NODECOMPRESS":
> Normally, when VSTORE verifies a compressed store media, it reads in
> each record and decompresses it.  This results in a thorough
> verification of the media by checking both the integrity of the data on
> the media as well as the correctness of the compression algorithm.  If
> the NODECOMPRESS option is specified, VSTORE will only read the records
> from the media. It will not decompress them.  This verifies only that
> there are no media errors on the media.

Note that this applies only to the Turbo Store ;COMPRESS option, not to
hardware compression done by the tape device itself.

Really all :VSTORE does is to read the data off the tape and throw it
away.  It does not do any comparison of the tape data with data on the
system.  So, for example, you can :VSTORE your backup set on a different
system if you want to.  You would get pretty much the same result from
just using :FCOPY to read through the tape to make sure there are no
media errors.

If you *are* using the ;COMPRESS option then :VSTORE performs the added
step of performing the software uncompress operation on the data read,
so that you know that the compression option didn't screw up and that
:VSTORE can read what :STORE wrote.

While :VSTORE can't guarantee that :STORE didn't mess up in some way,
it should give you confidence that the physical media is free of errors,
and that if there is going to be a problem restoring the data then it
won't be because there was a problem with the tape drive hardware during
the backup, which is what most of the discussion seems to have been
about lately.

One of the things we like to recommend is that after any important backup
you randomly choose one file that was backed up and try to :RESTORE that
file, preferably using a different physical tape drive.  Of course you
should do the :RESTORE into a scratch group rather than overwriting the
real file.  This simple step not only indicates that you have tapes that
are at least partially readable, but that things you *think* are going
onto the tape are actually getting there and that they can actually be
restored.  This process can identify lots of other problems that :VSTORE
might miss.

G.