Predictable, controlled change is core to successful implementations, and agile development can help you achieve just that.
BW/4HANA migration is complex and time-consuming, but it's also necessary. The new BW/4HANA database system offers many new capabilities for companies with growing data stores, but before you can take advantage of the platform, you need to migrate your legacy business data and structures. Any migration strategy involves significant costs and resources. When converting object types to BW/4HANA compatible types, manual adjustments to the BW design are necessary, as is an ABAP code review and modification.
When migrating between systems, it is recommended to break the migration into iterative development cycles. For in-place migrations, it is essential to do this as if you don't, then you'll be locking yourself out of making any future enhancements until all migrations are complete. The splitting of BW dataflows into manageable sizes is in line with the Agile methodologies that are often used in web development.
Keeping track of what work has been done, what's being worked on now, and what's scheduled for the next sprint or iteration is best practice. Smaller chunks of work mean more accurate estimates and faster delivery times.