Performance data hierarchy

Performance data is provided in a centralized hierarchy of the following objects to help provide some logical ordering: Node: A node represents a physical machine in the WebSphere cell. This is where the Node Agent resides in a Deployment Manager environment. Server: A server is a functional unit that provides services to the clients over a network. No performance data is collected for the server itself. Module: A module represents a resource category for which performance data is collected. As an example, these are Enterprise JavaBeans, database connection pools, J2C connectors, JVM runtime, Object Request Broker, relational resource adapter, servlet session manager, thread pools, transaction manager, and Web applications. Submodule: A submodule represents a fine granularity resource category under the model. Submodules themselves can contain submodules. An example of a submodule is the ORB thread pool, which is a fine granularity resource category under the thread pool module. Counter: A counter is a data type used to hold performance information for analysis. Examples of counters include the number of active enterprise beans and the time spent responding to a servlet request.

Each resource category (module) has a related set of counters. The counters contain values for performance data that can have an impact on system performance.

Modules can have instances, which are single instantiations of an object of a class. Counters can be assigned to any number of modules and instances. Figure 16-2 shows how this looks like in Tivoli Performance Viewer.

Figure 16-2 Tivoli Performance Viewer

Figure 16-3 shows the counter Avg Method RT assigned to both the enterprise beans module and the methods of the Container1.Bean1 instance. Figure 16-3 also shows a hierarchy of data collections that are organized for reporting to the Tivoli Performance Viewer.

Figure 16-3 Example performance group hierarchy

A subset of counters is available based on the instrumentation level chosen for the particular module or instance. Counters are enabled at the module level and can be enabled or disabled for elements within the module. For example, in the figure, if the Module Enterprise Beans module is enabled, its Avg Method RT counter is enabled by default. However, you can then disable the Avg Method RT counter for the Methods Beans1.methods and the aggregate response time reported for the whole Enterprise Beans module will no longer include Methods Bean1.methods data.

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