GNU tar has multivolume support. Useful for when the archive created is larger than a single tape's capacity. I hope that all of you understand that tape can also mean file, or DVD, or CD, etc.
From section 9.6 of the GNU tar manual:
Use --multi-volume (-M) on the command
line, and then tar will, when it
reaches the end of the tape, prompt
for another tape, and continue the
archive. Each tape will have an
independent archive, and can be read
without needing the other. (As an
exception to this, the file that tar
was archiving when it ran out of tape
will usually be split between the two
archives; in this case you need to
extract from the first archive, using
--multi-volume (-M), and then put in the second tape when prompted, so tar
can restore both halves of the file.)
emphasis mine
But do be careful about the exception! Maybe write out to files which you can check for size before writing the archive files to DVD. This could be done by a script. Or make the file size something smaller that 4.7G so that an archive that spans two DVDs never occurs.