The Database as a Networked Server - Implementing Database Security and Auditing - page 76

Figure 3.9
Selecting
communication
options for DB2
UDB (on
Windows).

3.4.3 Oracle networking layers

Oracle also supports many protocol options. Before looking at these
options and how you can configure them, let's briefly look at the network-
ing architecture, starting with how requests are communicated with the
server. Oracle has several configuration options that affect the server-side
process architecture. For example, Oracle may be configured to create a
process for each user connection or use a multithreaded configuration in
which only a thread (as opposed to a heavyweight process) is created per
user connection. In order not to overcomplicate the discussion here, let's
assume a multithreaded server (MTS) configuration. The networking archi-
tecture may differ slightly in other environments, but this is not significant.
In addition to the Oracle server processes, another process—the net-
work listener—is installed and is running on your machine. The listener is
part of Net9 (or Net8 or Oracle Net or SQL*Net—the name varies by ver-
sion). The listener is key in making the connection to the server. In fact,
when using shared servers and MTS, a client must connect through the lis-
tener even if it is running on the same host as the server process; if a client
cannot use the network libraries, it will connect using a dedicated server,
which puts unnecessary load on the database.
After communication has been initiated with the listener, the listener
assigns a dispatcher. An MTS can have many dispatchers, which are shared
among all clients and manage queues of requests. The listener assigns the
dispatcher with the lightest load, and the client continues all communica-