Database Connection without Database server name in the connection

HI

My question is about database connection on app server, IIS8.5/windows 2012 r2

When I look at the web.config file, I only see these two lines scattered in the file

<property name="connection.connection_string">Data Source=AppData;user=AppUser;password=******</property>


<connectionStrings>
      <add name="testconnection" connectionString="Data Source=AppData;Persist Security Info=True;User ID=appuser;Password=*******;Unicode=True;" providerName="System.Data.OracleClient"/>
    </connectionStrings>

When I look at the server, I don't see any ODBC connection defined on the server. I though that there must be a DSN named AppData, but there is none.

Since I don't see any ServerName for database in anywhere, then How the application knows which server to connect to for database access

any light on it?

Thanks all