Dear DHYANI
this is a bit my personal view on the topic - others may have different views on the issue.
Backing up database directly to a tape device seems the be outdated to me. It is my impression that RDBMS vendors tried to handle various tape devices but stopped their efforts in that direction quite some time ago. I think it got too complicated to mainaintain and document all the various tape options. Nowdays you dump to files in the file system or to a stream interface of a backup server like TSM or Legato Networker .
File dump devices are easy to setup for the DBA but require additional disk space and care needs to be taken that these file systems finally still do make it to some tape .
Storage Managers provide a stream API to the RDBMS software and hide the details of tapes and tape libraries - but typically the SM interface for your RDBMS is charged extra . Also Setup and operations of backups to a SM software directly is more complex and require cooperation sbetween the DBA and the administrator of the storage manager.
HTH
Tilman Model-Bosch