WebLogic Server
Instance
A WebLogic Server instance is a Java Virtual Machine
(JVM) process that runs the Java code. The
instance is the actively
working component, receiving client requests and sending them on to
the appropriate components, and sending the
processed requests back to the clients.
Weblogic server instance is combination of
admin server + manage server.
Administration
Server
A server is an instance of WebLogic Server that runs in
its own JVM, and the Admin Server is a special instance of
WebLogic Server designed for managing the domain rather than running applications. There is a
one-to-one relationship between domains and the Admin Server—an Admin Server belonging to Domain A can’t
manage Domain B.
You can deploy applications on the Admin Server, but
unless you’re operating in a purely developmental
environment, use the Admin Server strictly for performing management tasks, not for deploying any
applications. Although you can deploy applications on the Admin Server in a development environment, it’s a best
practice not to do so in a production environment
Managed
Server
Managed servers are the workhorses of WebLogic Server.
Any additional servers you create after the creation of the
default Admin Server are Managed Servers. The Managed Server contacts the Admin Server, only when
you start it up, to get the configuration and deployment settings. For this reason, you should
always start up the Admin Server before you start a Managed Server. Once a Managed Server starts running, it
operates completely independent of the Admin Server.
WebLogic
Server Cluster
A WebLogic Server cluster is a group of WebLogic Server
instances consisting of multiple Managed Servers that run simultaneously.
Machine
A machine in the WebLogic Server context is the logical
representation of the computer that hosts one or more WebLogic Server instances
(servers).
Node Manager
Node Managers help you remotely start, stop, suspend, and
restart Managed Servers.
Services
Following are some of the main services used in a
WebLogic environment:
■ JDBC (Java Database Connectivity) enables Java
programs to handle database
connections established
through connection pools.
■JMS (Java Messaging Service) is a standard API
that enables applications to communicate
through enterprise
messaging systems.
■JTA (Java Transaction API) specifies standard Java
interfaces between transaction
managers and the parties
in a distributed transaction system.
Development
and Production Mode
By default, WebLogic Server domains run in the
development mode using the Sun Java Development Kit (JDK).
In this mode, auto-deployment of applications is enabled and the Admin Server creates a boot.properties file automatically when you
start it up. You can also use the demo certificates for
Secure Sockets Layer (SSL) without any warnings from WebLogic Server. The development mode is
provided to get developers up and running quickly without having to worry
about advanced
deployment, configuration, or security issues.
In the production mode,
WebLogic Server defaults to using JRockit as the default JDK. In addition, you can’t use
the auto-deployment feature in production, and WebLogic Server issues warnings if you use the
demo certificates for SSL. In the production mode, you’re also prompted for usernames and
password when you start up the instances.
It’s easy to toggle
between the development and production modes
