[SunHELP] query on "tape" operation

[TAG DBA]

Solaris 8 on Sun E450
----------------------------------
I was trying to estimate how many sets of database backups can fit onto one 4 GB DAT tape.
One set approx is of size 1 GB. So atleast 3 sets should get copied to tape.
The command I type is :
$ tar cvf /dev/rmt/0cn $DUMPS

However during the third copy operation I got this error:

a ./archlogs_14_dec_01.Z 696322 tape blocks
tar: write error: unexpected EOF
Backing up export dump expTAG1SPZ_Fri_full.dmp.Z and log file /s0003/TAG1SPZ/expdumps/expbu_TAG1SPZ_14_dec_01.log ....
a expTAG1SPZ_Fri_full.dmp.Z 563396 tape blocks
tar: write error: unexpected EOF
Ending Backup Fri Dec 14 16:54:19 GMT 2001

Does it mean that the tape is full ???
Regards,
~aslam