Introduction to Oracle WebLogic Server for OC4J Users 3-5
Figure 3–4 Comparison of the Oracle WebLogic Server and OC4J Directory Structures
3.1.3 Understanding Oracle WebLogic Server Domains for OC4J Users
The following sections are designed to help OC4J users learn about the features and capabilities of Oracle WebLogic Server domains:
■
Basic Content and Organization of a Domain
■
Additional Facts About Oracle WebLogic Server Domains
3.1.3.1 Basic Content and Organization of a Domain
Depending on whether you are using 10g Release 2 10.1.2 or 10g Release 3 10.1.3, you organize your Oracle Application Server 10g environment in one of two ways:
■
In Oracle Application Server 10g Release 3 10.1.3, you organize your applications servers and OC4J instances into a cluster topology.
■
In Oracle Application Server 10g Release 2 10.1.2, you can add multiple Oracle Application Server instances into a farm and your OC4J instances into Oracle
Application Server Clusters.
Oracle Fusion Middleware 11g uses an entirely different mechanism to organize your environment. The Oracle WebLogic Server environment is grouped into logical groups
called domains. These domains consist of the following:
■
A single administration server, which is used to manage the domain.
■
One or more managed servers, which are used to deploy the Oracle Fusion Middleware Java components, as well as your custom Java EE applications.
In previous versions of Oracle Application Server 10g, you installed, created, and configured OC4J instances, and one or more Java Virtual Machines JVMs per OC4J
instance.
In Oracle Fusion Middleware 11g, you configure an Oracle WebLogic Server domain with one administration server and one or more managed servers to deploy your Java
EE applications.
3-6 Oracle Fusion Middleware Upgrade Guide for Java EE
3.1.3.2 Additional Facts About Oracle WebLogic Server Domains
The following sections provide more detailed information about Oracle WebLogic Server domains that can be helpful as you transition from an OC4J environment to an
Oracle WebLogic Server environment:
■
A WebLogic Server Installation Can be Used to Configure Multiple Domains
■
A WebLogic Server Instance Is Always Associated With a Single Java Virtual Machine Process
■
A WebLogic Server Instance Processes All Application Requests on the Same Port by Default
■
A WebLogic Server Instance Is Always Configured With an HTTP Listener and Does Not Support AJP
3.1.3.2.1 A WebLogic Server Installation Can be Used to Configure Multiple Domains As
shown in Figure 3–4
, the binary and configuration files associated with the OC4J instances you create are stored in a subdirectory structure inside the Oracle
Application Server 10g Oracle home the j2ee directory structure. Not only is this direct file system association required, but the relationship between the OC4J binaries
and the configuration of instances is at a per instance level.
In contrast, Oracle WebLogic Server provides a clear separation between the installed software and its different configuration instances. A single Oracle WebLogic Server
installation can be used to create multiple domains, each with a different set of servers.
By default, the Oracle WebLogic Server configuration wizard assumes that you will place the configuration files for each domain inside the user_projectsdomains
directory. However, the files associated with a domain can reside anywhere within the file system. For a WebLogic Server instance to run from a domain directory, the only
requirement is that the Oracle WebLogic Server directory must be accessible.
Note also that in the WebLogic Server model, the relationship between the WebLogic Server binaries and the configuration of instances is at a per domain set of instances
level.
3.1.3.2.2 A WebLogic Server Instance Is Always Associated With a Single Java Virtual Machine
Process OC4J executes on the Java Virtual Machine JVM of the standard Java Development Kit JDK. By default, each OC4J instance uses one JVM. However, you
can configure an OC4J instance so it runs on multiple JVMs. You can configure the OC4J instance in this manner using the numproc property or by using the Application
Server Control console.
When you configure an OC4J instance to run on multiple JVMs, the OC4J instance is essentially running on multiple processes. This can improve performance and provide
a level of fault tolerance for your deployed applications. However, multiple JVMs also require additional hardware resources to run efficiently.
There is no equivalent setting or capability in Oracle WebLogic Server. Instead, each server always runs on a single Java Virtual Machine. However, you can obtain the
same capability as the OC4J numproc setting by increasing the number of managed servers running on the same host and within the domain.
3.1.3.2.3 A WebLogic Server Instance Processes All Application Requests on the Same Port by
Default An OC4J instance uses a different set of listen ports for each protocol for which it can accept requests. OC4J uses the concept of OC4J Web sites to configure specific
HTTP, HTTPS, AJP, or AJPS ports or port range on each OC4J instance. Similarly,
