hmm perhaps this is not the most appropriate thread?

Anyhow, I have created a spanned archive using tar --tape-length

Any ideas how to reconstruct the original from the spanned archives?

--tape-length changes tapes after writing N*1024 bytes, so in the end it's basically a single tar file split onto several tapes. Copying all tapes to a large HDD and using cat is on way to join them, though I assume that tar will be able to read it's own tapes when the extract option is passed.
--multi-volume informs `tar' that it should create or otherwise operate on a multi-volume `tar' archive, being irrelevant if the volume is a tape or another device. In this case each volume is an independent tar file that can be used on it's own.
See 'info tar' for full documentation.

Linux

Are you suggesting for example that for a spanned set of 1.tar 2.tar 3.tar I should use the following:

tar -xM 1.tar 2.tar 3.tar

As I found that tar did nothing?

I believe M only works if you used --multi-volume. Did you try his cat technique?

In addition to cat, you will probably need -i because of the possible padding at the ends of the tape:Kevin Barry

Hi, OK cat did not work. I mean I did the following cat 1.tar 2.tar 3.tar > new.tar and the new.tar was created but the file new.tar failed to be extracted with a tar command following the cat. I noticed that new.tar was bigger than the original?

So I wonder if the tar command I used to archive the spanned set was at fault? *Sigh*

I will try tar with i.