DLT, AIT, and LTO are all tape formats. Oracle doesn't care what type of tape that you use.
These tape libraries typically are connected to your master backup machine either through SCSI or Fibre connections. You can then backup any other node from across the network. No, you don't need anything special for a SUN.
Veritas Netbackup works great with Oracle's RMAN. My Veritas sales guy said that Oracle (the corporation) uses Veritas to backup their entire enterprise. Legato is a nice product as well. A mini-version is included with 8i. Both work well for backing up Oracle through RMAN.
Most tape libraries don't come with sophisticated software. You will usually have to pony up some $$ for the backup software in addition to a robot license (license depending on your library size).
Some of the larger vendors of Libraries are StorageTek [url]http://www.storagetek.com/[/url], ATL [url]http://www.atlp.com/[/url], and Spectralogic [url]http://www.spectralogic.com/.[/url] You can also look to your Sun reseller for Sun badged ATL and StorageTek products.