Upgrade 4.6C to ECC 6.0 5 Tb Oracle 10g database takes too long

Hi,

We´ve just run an upgrade test with a 5Tb database and takes too long so our downtime will be more than 3 days, is there any documents that can lead us to get a better downtime some way

Any help will be appreciated.

HP-UX

4.6C (4.6D ext kernel)

Oracle 10g with 5Tb of data

Thanks