Oracle Application Server 10g Architecture and Administration - Application Server 10g Clusters and Farms and Database Tier (
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As just defined, a cluster is a collection of Application Server 10g instances that share identical configuration parameters, application deployment schemes, and J2EE applications. Clusters are used to enforce heterogeneity within the Application Server 10g instances. Hence, additions are commonly made to clusters when processing demands require additional Application Server 10ginstances in order to manage an increased demand at the application server level. Instances in a cluster are managed by the Application Server 10g Infrastructure, which provides an easy method for creating and maintaining clusters.
Clusters are used in conjunction with the Web Cache load-balancing algorithms, such that the load balancing at the Web Cache layer monitors all of the Application Server 10g instances in the clusters, and feeds work to the least-loaded Application Server 10g instance. Note that only J2EE and Web Cache components can be clustered, and that clusters must host a common set of J2EE applications.
Application Server 10g Farms
There is an important one-to-many relationship between an Application Server 10g instance and a metadata repository. Each Application Server 10g instance may have one, and only one, metadata repository, while each metadata repository may service many Application Server 10g instances.
From the Application Server 10g architecture point of view, a farm is a collection of Application Server 10g instances that all map to the same metadata repository. Because each Application Server 10g instance within a farm must contain the same metadata repository, all instances within the farm must share the same configuration and application membership information.
Database Tier
The standard Application Server 10g relational database (or any other database) resides in the database tier. The function of the database tier is to provide the application with persistent storage. The Application Server 10g also contains a special instance called the Infrastructure that uses a 10g database to store metadata. This database is more correctly in the application server tier since it does not provide persistent storage for the application. The application server provides a method to place the Infrastructure database schema into a database in the database tier; however, best practices will still recommend that the Infrastructure database support only the infrastructure and be separate from the customer database for performance reasons.
The following components have a tight integration with the Oracle Infrastructure database:
- Oracle Application Server Portal -- Web screen component definitions are stored inside the Oracle Infrastructure database.
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Oracle Reports -- Report specifications are stored inside the Infrastructure database.
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Oracle Application Server Discoverer -- Discoverer metadata is stored inside the Infrastructure.
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Oracle Application Server Personalization -- The Infrastructure database is used to store consumer group information and historical page viewing (referrer statistics) information.
Component Overview
Now that you have an overview of the architecture of Application Server 10g, let’s continue our tour with a review of the components. Not all shops will have all of these components installed, but Application Server 10g allows for any or all of them to be created inside the architecture.
Application Server Portal
Like the non-Oracle tools such as Dreamweaver and Microsoft FrontPage, Portal allows developers to create and deploy web content. The important difference is that developers can include dynamically created, personalized web pages from multiple data sources using Portlets. The Portal product provides the following features:
- Portal page creation, management, and maintenance
- Assembly of web content from multiple sources using Portlets
- Web page content that contains data retrieved from a database
- Publishing facilities using easy wizards
- Advanced features such as text searching (via Oracle Text) and wireless support via XML and HTML interfaces
These components fit together into an architecture that allows developers to quickly create and deploy web page content. Figure 1-8 depicts a Portal administrator defining the Portlet content and the content for the basic web pages. At run time, Portal users access these definitions to create dynamic publishing content, using the Portlet definitions, the web page definitions, and data from the Oracle Database.
It is beyond the scope of this book to examine all of the content delivery features of Oracle Application Server Portal. For complete information on using Portal, see Oracle9i Application Server Portal Handbook by Vandiver and Cox (McGraw-Hill/Osborne, 2001).
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 This chapter is from Oracle Application Server 10g Administration Handbook, by Garmany and Burleson. (McGraw-Hill/Osborne, 2004, ISBN: 0072229586). Check it out at your favorite bookstore today. Buy this book now.
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