Changing BW source system

Hi Experts,

We have 4 system landscape with DEV, QUALITY, TEST and PROD BW environments with
corresponding ECC environments. There is a requirement where ECC TEST system
will be out of landscape for some time and we need to connect ECC QUALITY
environment with BW Test.

Please let us know what points should be considered while changing source system
connection. It would be great if you could share challenges faced post source
system change in such scenarios.

Thanks!