1. When application try to connect, uses Config file (Configuration file--Resides in application server). Config file (.txt) should contains SQL Server instance name + user name [service account name--DBA team should add the account into SQL Server under security] + Password [Strong]
Application use all these details from Config file and point connection to SQL server database
Real time points:
> Any business 2 data centers maintains called PRODUCTION and DR data center.
> Always distance between data centers should not be more than 50 KM.
> Few people always work inside the data centers.