Oracle Application Server 10g Architecture and Administration - Command-Line Interfaces or OEM?
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As we have already noted, administrators have two choices for managing Application Server 10g—the OEM console GUI or the command-line interfaces. Using the OEM console, the GUI will issue the appropriate commands without your having to memorize the syntax. On the other hand, many experienced Application Server 10g administrators find that the command-line interface offers a full range of administration commands.
Of course, some tasks must be done from the command-line interfaces. For example, you cannot use OEM until the OMS is started, so you must issue the emctl start oms command before you can use OEM. Internally, it makes no difference whether you use OEM or a command-line utility to manage Application Server 10g. This is because the OEM console uses DCM (the dcmctl utility) to make configuration changes, and to propagate configuration changes and deployed applications across the cluster.
CAUTION: If you use the Infrastructure and you manually edit the configuration files, you may introduce corruption into the Infrastructure. This is true for both v9.0.2 and v9.0.3. Be sure to shut down the Enterprise Manager website (emctlstop) before using dcmctl to change configuration. If/when both are used" at the same time," there is a strong possibility that the Infrastructure data may become corrupted, and you may have to reinstall Application Server 10g. The dcmctl-updateConfig command can be used to notify the environment that config files were updated so that the changes are properly picked up. This requirement will be referenced throughout the book.
Let’s start with a quick tour of OEM for Application Server 10g and then review the command-line interfaces.
Managing Application Server 10g with Enterprise Manager The Enterprise Manager console is the central management component for Application Server 10g. From a page of the EM central console, you can manage most of the areas of Application Server 10g on multiple servers.
If you have installed the Infrastructure component of Application Server 10g (iasdb database repository), then the default EM console page will be the EM Farm page. The Farm page is the highest level of the EM pages and is used to administer all instances within your Application Server 10g configuration. Let’s quickly review the component hierarchy from the bottom up:
- Instances -- Each J2EE app server or infrastructure is called an instance (not to be confused with an Oracle Database instance, which is quite different).
Clusters -- A cluster is an arbitrary collection of instances.
Farms -- A farm is a collection of instances and clusters that make up your Application Server 10g system and share a common repository database (iasdb).
Each farm may have many clusters, each cluster may have many instances, and each instance may have many Application Server 10g components. It is your job as the administrator to configure your components, instances, clusters, and farms according to the processing requirements of your application.
The purpose of the EM Farm page is to serve as the master console and display summary information about each instance and cluster within the farm (Figure 1-13).
Remember, each instance within the Farm page is an independent J2EE app server or an infrastructure, and the Farm page allows you to drill-down and see the details for each instance using the EM Instance Manager page. Using the EM Farm page, you can also define new clusters and assign instances to clusters. In Application Server 10g parlance, a “standalone” instance is a J2EE app server, belonging to a farm, which has not been assigned to a cluster. A cluster is two or more identically configured app server instances. To assign an instance to a cluster, you simply choose it and click the Join Cluster button.
Next, let’s step down one level and look at what you see when you drill-down into an instance and see the EM Instance Manager page.
 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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