Backup Oracle Dedup

Hello all Forum 

I have a Netbackup Appliance 5220 where there are backups of VMware Snapshots and Oracle DB. 

The jobs VMware backup Full and Incremental the dedup being done, seems to have a great result, an excellent rate for a sign. 

Already in my backups Oracle Database, the rate of Dedup is only 1%. 
I wonder what can I do to increase that rate and I can have more space in my Appliance. Backups are many daily and my whole 30TB fills easily. 

Can anyone tell me where I can start to check and improve it? 

Thank you all. 
Juliano Moreira