About Server and Client Processes

About Server and Client Processes
In addition to background processes, Oracle Database creates server processes that
handle the connection requests of user or client processes. A user connection is
composed of the following distinct pieces:
■ A client program acting on behalf of the user, such as Oracle Enterprise Manager
(Enterprise Manager), SQL*Plus, or an application
■ A server process that handles the connection to the database on behalf of the client
program, and that performs much of the work for the client program, such as
parsing and running SQL statements, and retrieving and returning results to the
client program
Server processes can be either dedicated or shared. When server processes are
dedicated, Oracle Database is running in dedicated server mode. When server
processes are shared, Oracle Database is running in shared server mode. In dedicated
server mode, each client process has its own server process. Although a dedicated
server process is good for long-running queries and administrative tasks, an idle
process or too many dedicated processes can result in an inefficient use of resources.
Using shared server mode eliminates the need for a dedicated server process for each
user connection, requires less memory for each user connection, and enables more
users to access the database. Shared server mode is more efficient at supporting
multiple client programs making frequent short-running queries.
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