Oracle Network Administration - Oracle 10g Database Administration Concepts and Implementation Made Simple - page 205

Figure 8-4: No Service Name or in other words no tnsnames.ora file.
The purpose of tnsnames.ora file is that it contains the name resolution
of Net Service Name.
Figure 8-5: No listener process or in other words no listerner.ora file.
We will first create the listener on the machine running Oracle Server
using ONM.