Java Tools Tutorials - Herong's Tutorial Examples - v6.21, by Dr. Herong Yang
jmap - Generating Heap Dump File
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:
herong> java -Xmx24m GarbageCollection Free/total memory: 23725256 25034752 22710400 25034752 21618728 25034752 20523584 25034752 ... (Start another command window.) herong> jps -l -m 10672 GarbageCollection 1256 jdk.jcmd/sun.tools.jps.Jps -l -m herong> jmap -dump:file=GarbageCollection.map 10672 Heap dump file created herong> dir *.map 22,306,616 GarbageCollection.map
So the heap dump file, "GarbageCollection.map", is a snapshot of all heap objects used by the running GarbageCollection.java process. The size of the heap dump file should be the same as all currently allocated objects in the heap.
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