univac tape format

From: Sean Case <gsc_at_zip.com.au>
Date: Thu Jan 4 06:04:21 2001

>We have got some UNIVAC 9-tracks tapes we are trying to read.
>(The tapes were written in 1982, so it is a possibility the data is lost.
>Our UNIVAC 110xs are long gone.)

First of all, you might want to try asking this question on the
comp.sys.unisys newsgroup. If nothing else, you may find someone with the
current version of these machines (Unisys 2200 or Unisys ClearPath IX) who
can do the conversion for you.

>What is the UNIVAC tape format?
>(I have not found any info on the net yet)

It depends on what's on the tape.

The 1100 series are 36 bit machines. The usual tape format has two words
packed into nine tape frames. MSB of the first frame would be the MSB of
the first word, and LSB of the last frame would be the LSB of the second.
(I think.)

Text is usually encoded in ASCII, using nine bits per character. Text
files are in a variable length record format, with a file header that
starts with octal 50 in the high order six bits of the first word, and
a record header word on each record.

The actual text may be wrapped inside various levels of archive, but if
you see long stretches of readable ASCII, you've found the actual meat.

(There may also be some text encoded in an older six-bit character set.
That seems a bit old-fashioned for 1982, but you never know.)

Now for the good news. If the tape was _intended_ to be read by a non-
Univac machine, then it may well have straight ASCII (or even EBCDIC)
text recorded one character per frame with fixed length records.

A dump of the first few blocks on the tape, as well as an idea of what
sorts of block lengths there are on the rest of it, would be a great
help in trying to guess the format.

>We are trying to read it on a VMS system with 9-track TSZ07 streamer.
>(TSZ07 is SCSI, 1600/6250 bpi. Suppose it is ANSI too)
>Is the hardware compatible enough?

Should be, assuming the tape is actually in one of those densities.
Making sense of the contents may be harder.

>If it is, how do I read it? (Got a Unix utility called copytape, so the
>streamer may eventually be moved)

I don't know of a Unix utility that can cope with all the variations of
1100 series tapes. The easy way is definitely to get someone with a
compatible machine to read it. (Is your site still on speaking terms with
Unisys?) The other option is to find out exactly what format your tape is
in, and knock something together to read it.

Sean Case
Received on Thu Jan 04 2001 - 06:04:21 GMT