Hi,

From the oracle error description, something is trying to read the datafile which is offline. If you want to make cold backup, why dont you shutdown the database and restart when it finishs? You can put the procedure in the script. Or if you want to make hot backup while database is open use "alter tablespace tablespacename begin backup;" copy the file and when it finishs, end the backup with "alter tablespace tablespacename end backup;". You could also put this in script.

regards,
feroz