Session Management - Oracle 10g/11g Data and Database Management Utilities - page 156

User sessions in a dedicated server
architecture
When a user requests a remote connection to the database it must first contact the
listener. The listener redirects the request to the Oracle Instance. This will spawn a
new Oracle Server Process, which from now on will be the process who will interface
the user with the database; if the connection to the database is local to the machine,
it may be established across the network or by Inter - Process Communication ( IPC ),
and the Oracle server process will be spawned too. This Oracle server process will
be assigned to the user for the whole time the user remains attached to the database.
The new user session will be assigned a Serial Number and a Session Id. These are
the numbers used to uniquely identify a user connected to the database. The serial
number guarantees that session-level commands are applied to the correct session
objects in case a new session is started with the same SID. A user session can be
initially monitored with the V$SESSION dynamic view.

1

Listener

PMON

2

3

4

User
Process

Server
Process

Database

Dedicated server architecture

The PMON background process registers the Oracle instance against the Listener
(in a self registration configuration), PMON registers information about dedicated
server processes with the Listener . A User Process starts a connection against the
Oracle instance by looking for the Listener , the Listener redirects the user process to
the oracle Server Process and the dialog will be conducted from now on between the
oracle server process and the user process. For each active connection in a Dedicated
Server Architecture there will be one oracle Server Process on the host machine.