What is difference between Netbackup 6.5 to 7.5 in Architecture Level?(Not features)

Hi to all,

What exactly Changes done in Netbackup 7.5 in architecture level when compare with Netbackup 6.5? Some one said ,Basic architecture is same for Netbackup 6.5 and 7.5 But in Netbackup 7.5 Image database resides in NBDB, Is it correct?Can any one Plase give exact difference between in Netbackup 6.5 and 7.5?( Not features)

Thanks

Krishna.