Not all migration methods apply to all migration scenarios. Many of the migration methods apply only if specific characteristics of the source and destination databases match or are compatible. Moreover, additional factors can affect which method you choose for your migration from among the methods that are technically applicable to your migration scenario.
Some of the characteristics and factors to consider when choosing a migration method are:
On-premises database version
Database service database version
On-premises host operating system and version
On-premises database character set
Quantity of data, including indexes
Data types used in the on-premises database
Storage for data staging
Acceptable length of system outage
Network bandwidth