App Server Tier, Partitioning - Oracle

The core of Application Server 10g, along with a host of other tools and products, is in the app server tier. The central components are the Application Server 10g instances, and these instances support the Oracle Containers for Java (OC4J). The OC4J container hosts the application’s Enterprise JavaBeans, providing security, naming, and connectivity support. In addition to the Application Server 10g instances, the app server tier contains separate components for the following functional areas:

• Oracle Portal -- This component allows for the fast definition and deployment of a dynamically created content-based web site.

• Oracle Discoverer -- This component allows for the easy end-user query implementation.

• Oracle Forms Server -- This component is used to format, deploy, and render end-user presentation pages, based on data in an Oracle Database.

• Oracle Personalization -- This component provides personalized URL referrer tracking and a facility for creating customized web pages, depending upon the user and his or her web page viewing history. The web page history is kept in Oracle Databases.

• Oracle Wireless -- This component allows for communications between Application Server 10g and wireless devices such as PDAs and cell phones. Wireless dynamically reformats information to display correctly on the limited screens of most wireless devices.

• Oracle Reports Server -- This component allows for the fast deployment of reports, documents, and spreadsheets, all using data from the Oracle Database.

• Single Sign-On (SSO) -- This is a complete authentication system for identifying users, managing roles and web services, as well as functionality for Java and portal security.

• Oracle Internet Directory (OID) -- This LDAP-compliant directory service provides centralized storage of information about users, applications, and resources in your enterprise.

• Metadata repository (Infrastructure) -- This critical component is sometimes referred to as the Infrastructure. It stores Application Server 10g metadata and allows for a common management interface between multiple instances of Application Server 10g and its other components.

• Oracle Management Server (OMS) -- This component of the Enterprise Manager console allows for managing the Application Server 10ginstances, databases, and other applications.

• Oracle Application Server TopLink -- This component provides object persistence for Java information. TopLink contains the mapping interfaces to translate the Java structures into relational tables, thereby making Java persistent across independent executions.

These components are partitioned within the Application Server 10g app server layer, allowing administrators flexibility in the creation of multiple Application Server 10g instances.

Partitioning with Farms and Clusters

Application Server 10g provides several levels of collections within the App Server layer:

• Instances -- An instanceis defined as a collection of processes required to run a component within an application server instance. An instance is made up of one or more Java containers and the structure needed to support them. The Application Server 10g Infrastructure is an instance with a supporting database to store metadata.

• Clusters -- A clusteris an arbitrary collection of instances that are part of the same farm and also share a common configuration and J2EE applications.

• Farms -- A farmis a collection of instances and clusters that make up your Application Server 10g system and share a common repository infrastructure.

In sum, a farm is any related group of Application Server 10g instances sharing a repository, while a cluster must share a common definition and J2EE applications (Figure 1-7). Any Application Server 10g architecture may have many farms and many clusters defined within the system.