Generating Heap Dump File with 'jmap'

Java Tool Tutorials - Herong's Tutorial Notes

Dr. Herong Yang, Version 5.11

Java Tool Tutorials - Herong's Tutorial Notes

∟Generating Heap Dump File with 'jmap'

This section provides a tutorial example on how to generate a heap dump file with the 'jmap -dump:file=name' command. A heap dump file contains all heap objects of JVM process.

The second function of the "jmap" tool is to generate a heap dump of a given JVM process with the "jmap -dump:file=<filename>" command:

C:\herong>\Progra~1\java\jdk1.6.0_02\bin\java 
   -Xms24m -Xmx24m GarbageCollection

Free/total memory:
23725256   25034752
22710400   25034752
21618728   25034752
20523584   25034752
...


(Start another command window.)
C:\herong>\Progra~1\java\jdk1.6.0_02\bin\jps -l -m

764 GarbageCollection
1204 sun.tools.jps.Jps -l -m


C:\herong>\Progra~1\java\jdk1.6.0_02\bin\jmap 
   -dump:file=GarbageCollection.map 764

Dumping heap to C:\herong\GarbageCollection.map ...
Heap dump file created


C:\herong>dir *.map

  12:08 AM        19,816,895 GarbageCollection.map

So the heap dump file, "GarbageCollection.map", is a snapshot of all heap objects used by the running GarbageCollection.java process.

Heap dump files can be browsed by the heap dump browser, "jhat", as described in the next section.

Table of Contents

About This Book

Java Tools Terminology

Installing J2SE 1.6.0 on Windows

Installing J2SE 1.5.0 on Windows

'javac' - The Java Program Compiler

'java' - The Java Program Launcher

'jdb' - The Java Debugger

'jconsole' - Java Monitoring and Management Console

'jstat' - JVM Statistics Monitoring Tool