Figure 9-2 Early Indicator of Possible Memory Leak Using Heap Monitor Display

HPjmeter uses the long term linear upward trends in the heap size after garbage collections to calculate the presence of memory leaks.

Short-term increases in heap size are normal. HPjmeter measures this rate in MB/hour.

HPjmeter does not report a leak in situations in which the heap size increase is only temporary, or in situations in which the slope of the fitted line is too small to raise an alarm.

However, sometimes a healthy Java application is diagnosed with a memory leak. When the heap size returns to its previous range, such an erroneous diagnosis is revoked, reverting to its original state.

Leak detection accuracy improves over time, so if a memory leak alarm fluctuates on and off, or in value, you should base your analysis on the present alarm state.

With high leak-rate, you can consider having the IT administrator start another JVM and stop the old one in a controlled way, in a clustered environment, when the garbage collection percentage becomes excessive. What is considered excessive depends more on the rate of change of garbage collection percentage or the estimated number of minutes before the heap will run out.

Related Topics

•Java Collection Leak Locations Alert (page 111)

•Confirming Java Memory Leaks (page 43)

•Determining the Severity of a Memory Leak (page 43)

•Memory Leak Applications (page 33)

•Basic Garbage Collection Concepts (page 87)

Tapping in to Standard Management of the Java Virtual Machine

HPjmeter retrieves information about the state and activity of the JVM (Java 1.5 or later) on HP-UX by making use of the JSR-174 API . HPjmeter collects information about MXbean notifications, attributes, and operations for display in the JMX viewer. It uses control aspects of the API to allow you to see and manipulate your own MBean attributes and operations in real time.

190 Understanding How HPjmeter Works