How to import the contents of an Oracle database into Visio to create an Entity Relationship Diagram

You can't do that in Visio. However, you can reverse engineer a database using Visio. The answer to the question below should help you.

How can I import the contents of an Oracle database into Visio to create an Entity Relationship Diagram?

your database is running in archivelog mode. An initial backup + archives allow you to recover your database to any point in time between the backup and the last available archivelog file. If this is a big import you are most likely going to make a backup afterwards. If you have no need to recover the database to a state between now and the previous backup, you could use rman to delete the archived log files, freeing space so the archiver can continue. An other option is to increase the db_recovery_file_dest_size parameter that could be in place since you claim to have plenty of space available.

sqlplus / as sysdba
show parameter db_recovery_file_dest_size
alter system set db_recovery_file_dest_size = {A_BIGGER_SIZE}

or

rman target=/
delete archivelog all;

don't forget to make a backup, deleting the archives makes recovery impossible.