[Info-vax] Backup TK50 tapes

[Paul Sture]

In article <kgh0n3$gjv$1 at Iltempo.Update.UU.SE>,
 Johnny Billquist <bqt at softjar.se> wrote:

> On 2013-02-25 15:24, Paul Sture wrote:
> > In article <kgdca9$jnv$1 at Iltempo.Update.UU.SE>,
> >   Johnny Billquist <bqt at softjar.se> wrote:
> >
> >> On 2013-02-23 16:47, Stephen Hoffman wrote:
> >>> Last time I did a dd with a tape ⤲ which was admittedly a very, very
> >>> long time ago, as serious use of bootable tape media has been shunned
> >>> for years ⤲ it didn't deal at all well with the differing block sizes,
> >>> which caused all sorts of problems when replicating the media.   I don't
> >>> know of an automatic tool to do that, other than rebuilding the kit as
> >>> DEC VMS engineering once did, with the various tools in OpenVMS.
> >>
> >> Right. dd just is the wrong tool. It's really easy to throw together
> >> your own small program to actually read blocks, and keep the block
> >> structure around. But no standard utility for this exists. (On Unix - as
> >> far as I know.)
> >
> > COPY on a Files-11 mounted tape got me most places I wanted to go here,
> > although back in the V2 to V3 era you had to mount the tape with a
> > sufficiently large block size to cope with files whose block size
> > exceeded the default for MOUNT of 2048.
> >
> > If COPY failed (though I don't recall it doing so), I had plenty of tape
> > reading and writing programs I could use as a template.  COBOL was
> > excellent for this stuff; you just needed to understand that each COBOL
> > READ of a tape mounted foreign would retrieve a whole tape block and it
> > was up to you to unpack into records to process typical data files.
> > Properly labelled tapes had the record and block size info in the
> > headers.
> 
> This is one of those times where my VMS ignorance shines through. For a 
> PDP-11 tape, COPY will not do, even if you mount the tape on VMS.
> Yes, it is ANSI labeled. Yes, the savesets are all there.
> However, the boot block of the ANSI tape is not visible as a file.
> 
> But maybe it differs on a VAX with VMS?

My memory isn't shining here, but I'll agree with other posters that 
tape to disk to tape wasn't the same as tape direct to tape.  I also did 
what another poster mentioned and experimented with the ordering of 
files on TU58s to get faster boot times.

> If you don't know/understand enough about the tape formet as such, I can 
> explain the problem in more detail. But only with certainty from a 
> PDP-11 point of view.

-- 
Paul Sture