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7.2.4 Using models and clones

7.2.4 Using models and clones

A model is a template for creating copies of a server or process instance, such as an application server or servlet engine. The copies are called clones. The act of creating the clones is called cloning.

Cloning and modeling allows identical copies of objects (such as application servers, servlets, and so forth) to be created. A system administrator first creates a model that abstractly represents an object. From this model, one or more clones can be created. The clones represent real application server processes; when first created, they are identical to the model in every way.

Changes to a model are propagated to its clones when the clones are restarted. You can efficiently administer several copies of a server or other resource by administering its model.

Models and clones can be created for objects at any level of the containment hierarchy. However, it is recommended that you create them for application servers.  A model contains the objects that are deployed into the object from which it is created. For example, individual enterprise beans can be modeled and cloned without cloning the container in which they are deployed. Clones of containers include the enterprise beans that are deployed into the modeled container. Clones of application servers include the containers and enterprise beans that are deployed onto their model, and so forth.

Modeling and cloning objects at different levels of the application server containment hierarchy (from individual servlets and enterprise beans to entire application servers) gives administrators a great deal of flexibility for implementing and administering applications. For example, a system administrator can create models of an application server, servlets, containers, and enterprise beans; adjust the properties of the models to optimize the performance of these objects; then deploy them by creating and starting clones from these models.

Working with models and clones

The basic procedure for using models and clones is as follows:

  1. Create the original instance of the object that you want to clone (such as an application server, servlet, or enterprise bean). Configure it exactly as you would like it. For example, you can configure an application server to meet specific performance goals.
  2. Create a model of the object by using the administrative console. Making the original instance a clone is recommended but not required. The original instance can remain freestanding.
  3. Create clones from the model.
  4. When changes are necessary, apply them to the model, which in turn modifies the original instance (which is now a clone) and the other clones.

Determining which resources can be cloned

To determine whether a resource can be cloned, right-click the resource in the Topology tree to display a pop-up menu. If the menu contains a Create -> Model option, the resource can be cloned.

Resources that can be cloned include the following:

  • Application servers
  • EJB containers
  • Enterprise beans
  • Servlet engines
  • Servlets
  • Web applications

Although WebSphere Application Server supports cloning at all levels of the containment hierarchy, it is recommended that you create models and clones at the application server level. The cloned application server contains clones of the enterprise beans, servlets, and other resources that are deployed onto it. Creating models and clones at the application server level simplifies their administration. It is easier to manage the clones of an application server than to individually manage clones of all of the resources contained in it.

Go to previous article: Workload management for administrative servers Go to next article: Cloning for workload management, failover, and scaling

 

 
Go to previous article: Workload management for administrative servers Go to next article: Cloning for workload management, failover, and scaling