the beauty of informix ontape-onbar against oracle rman

Dear Informix gurus , As for the man who started to work with oracle 9i after 7 years of informix experience , i want to share my latest problem with oracle and get some suggestions / corrections from you , the gurus of informix - oracle . I work with a datawarehouse system which runs on Linux -itanium processor-oracle9i and emc disk array . I want to take full archive of my system(in informix term) But i was told that rman cant backup data directly to tape without a third party softare like legato or etc. But those third parties have not released a version on itanium yet. So , i have to take backups to disk than transfer to tape but within current situation it is impossibe for me to find such a large disk area. I know that and used lots of time ontape,onbar for data archives , they can directly write to tape , (even when the tape device is a remote one , this is also my case) , but why oracle cant do this ? Or is there anyone who can tell me the fact about this? Kind Regards, hope