well i have two servers. server A is the running server. server b is a standby server. server b is more powerful. downtime is a no-no

i plan to replicate the database on server B.

Problem: several programs are using the DB. I need to manually edit the source code to run using server B and manually configure each client to use server B as their database. If i will run both servers as replicated servers and those programs accessing the two servers

1. would those programs run as if they are seeing only one database?
2. would consolidation of data run smoothly and not encounter any problems?