Database Software

The shop where I am a player (in the PM team) is implementing a data warehouse migration from data center A to B.

Overall Landcape:
* There are multiple projects in flight in the DW ecosystem which must be unimpacted (to the extent possible) during the migration.

Overall Manadate:
"Preserve status quo during the migration (*) while not impacting user experience.. (* : no major reengineering efforts from DW context)

Current State:
* Large knowledge gap of the current infrastructure in data center A. No documentation. Lack of tribal knowledge. Shop is filled with vendors (via staff augmentation). Frequent attrition of full-time employees, contributing partially to the knowledge gap.


*ASK*:
Is there a comprehensive way, via a (semi-)automated tool (either at the app layer or network layer) to identify all the source systems from which data is pulled into the landing zone of the DW?

If not, what is a structured process to systematically accomplish this (without managing by "wandering around")?

Thanks for any feedback.