This is a text description of Figure 1-1, "The Gateway Architecture".
This illustration of the gateway architecture is adequately described in the "Architecture" section of the chapter, which is presented before the figure.
The Client is shown connecting to an Oracle database by means of Oracle Net or by means of a local connection.
The Oracle database connects to the gateway instance (Oracle Database Gateway for DRDA) by means of Oracle Net or by means of local connections (or by one of each - any combination is possible).
The gateway instance connects through the network to the DRDA server.
The purpose of this figure is to show that the Oracle Database Gateway for DRDA can connect an Oracle database to a non-Oracle database. Connection options include Oracle Net, local connections, and TCP/IP links.