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\jdk1.8.0\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\jdk1.8.0\bin\jps -l -m

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


C:\herong>\Progra~1\java\jdk1.8.0\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.

Last update: 2015.

Table of Contents

 About This Book

 Java Tools Terminology

 Installing Java 8 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

JVM Troubleshooting Tools

 JVM Troubleshooting Tools in JDK 1.5

 'jinfo' - VM Option Value Checker

 Changing HotSpot VM Option using 'jinfo'

 'jstack' - Stack Tracer to Generate Thread Dump

 What Is a Thread Dump?

 Java Thread Deadlock Demo Program

 Detecting Java Thread Deadlocks with 'jstack'

 'jmap' - JVM Heap Dump Tool

 Printing Histogram of Java Object Heap

Generating Heap Dump File with 'jmap'

 'jhat' - Java Heap Analysis Tool

 Starting 'jhat' Web Server on a Heap Dump File

 Listing Instance Counts of All Classes

 Browsing Object Instance Values

 Object Query Language (OQL)

 Searching for Instances with OQL Statements

 jvisualvm (Java VisualVM) - JVM Visual Tool

 'jar' - The JAR File Tool

 'javap' - The Java Class File Disassembler

 'keytool' - Public Key Certificate Tool

 'native2ascii' - Native-to-ASCII Encoding Converter

 Outdated Tutorials

 References

 PDF Printing Version