MediaBin assets migration from 4.6.2 to 8.1

System

Hi,

We are planning to upgrade Mediabin from 4.6.2 to 8.1.
I am confident of installation, but not sure about migrating existing assets/user permissions from old to new MediaBin.
I don't find any document related to asset migration and upgrade steps in installation document is not so helpful.
Can any one help me in sending the migration script/document.
Our existing MB database is Oralce 11G. And plannig to install 8.1 in MS SQL.
Will there be any issues? please suggest.

Thanks,
Shravan