Explanation
https://docs.oracle.com/en/cloud/paas/exadata-cloud/csexa/considerations-migrating-premises-database-dbcs.htm Some of the characteristics and factors to consider when choosing a migration method are:
* Source and target database versions
* Source platform and operating system
* Source database character set
* Quantity of data, including indexes
* Methods available for data transportation
* Database features and data types used
* Storage for data staging
* Acceptable length of system outage
* Network bandwidth