You have file system permission on both the 11g and 12c systems.
You have configured the WebLogic authentication chain to enable the 11g users to sign in to the 12c domain. For more information, see Configuring Authentication Providers in Administering Security for Oracle WebLogic Server 12c (12.2.1).
You have stopped the 12c BI instance, in case it is running. The BI instance should not be running before migrating content into the new 12c instance.