JARM in the VM Container
Use
JARM stands for Java Application Response time Measurement and is used to measure Java application requests. To do this the Java code in an application is instrumented in such a way that it can later be measured at runtime. As instrumentation is part of the application, the instrumented parts can also be measured in production systems. This can help developers find out the cause of an errors, and analyze performance.
Features
JARM provides a Java API divided into the following parts: code instrumentation, overview of results, and configuration. The two last parts of the API can be accessed almost entirely from the VMC system administration (transaction SM53).
Instrumentation
JARM instrumentation is based on the definitions below:
● A JARM request is the object that is measured. A JARM request is executed in a thread. Multiple requests cannot be nested in the same thread.
● A JARM request consists of components that represent the units to be used. Unlike requests, components can be nested. To keep the code routes to be measured coherent, and the monitoring overhead small, you should not chose granularity that is too fine.
● Each component can contain various actions. An action is a string that describes the activity in the component and is output in the trace.
The graphic below shows the difference between requests (R1, R2, etc.) and components (C1, C2, etc.) in a Java program.
In this example two requests are measured: Request R1 that first contains the mathematical calculation and then the new thread and its coding up to the join. Request R2 consists only of the run function, which contains a for loop (c4). R1 then contains components c1 (the while loop) and c2. Component c1 for its part contains n times the component c3 (the mathematical function).
Overview of the Measurement Results
You can display the Measurement Results in the VMC system administration (SM53).
Configuration
The JARM configuration can be defined and changed for the active instance at runtime. JARM configuration can be set in transaction SM53. For more information see Displaying and Changing JARM Settings.