What's the best way to clone Oracle 11.0.2.2 database in Solaris to oracle 12.2.0.2 database in Linu

Recently I had to create copy of an existing 11g database to Oracle 12 database from Solaris to Linux server. For this I created a new 12 database in Linux then used Data Pump for data migration from old database to new database. It worked fine but it took about 9 hours and time for creating and loading  few tables that import failed to create. Because 9 hours downtime to upgrade and migrate the production database from 11g in Solaris to 12 database in Unix is not something easily affordable in production environment, can someone please give an insight on