Oracle 11g to PostgreSQL 10 - Database Migration

Hello All,

We have a requirement to migrate from Oracle(Multiple versions) – 11gR1,11gR2,12c to PostgreSQL 10 to private cloud of customer  in context to that –

1.       Please let me know the best practices for migrations- any documents ,links etc.

2.       Open source tools for migration.

3.       OS and kernel parameters as per PostgreSQL standards for DB instances.

4.       Design and planning for PostgreSQL configurations.

5.       If Ora2pg tool is enough for migration?

Thanks

Soumik