Below a workaround is shown how to “duplex” archivelog backups between disk and tape:
Backup on disk (normal way):
backup device type disk archivelog all;
Immediately backup on tape:
backup device type sbt archivelog until time 'sysdate' not backed up 2 times;
This backup command backs up all archivelogs, that are not backed up twice, so all which are backed up with the first command. As in the first backup command a logfile switch is included, between the two backup commands, no logfile switch should occur, otherwise “duplexing” does not work. The until time clause in the second command is added to prevent RMAN from another logfile switch, which would lead to different contents of the backups. And this clause does not filter anything, because sysdate means date and time when issuing the command.