System dump

When a JVM crash occurs, the JVM requests the operating system to generate a system dump.

A system dump consists of all the memory that is being used by the JVM; this includes the application heap, along with all JVM and user libraries. System dumps allow the IBM® service personnel to look at the state of the JVM at the time of crash, and help them with the problem determination process. Because a system dump contains all of the memory allocated by the JVM process, system dump files can be very large.

You can find the location of the generated system dump in the output that is displayed in the console after the crash. Here is an example of the output:

Unhandled exception
Type=Segmentation error vmState=0x00000000
Windows_ExceptionCode=c0000005 J9Generic_Signal=00000004 
ExceptionAddress=000007FFFF2D90C2 ContextFlags=0010001f
Handler1=000007FFFF4EEF80 Handler2=000007FFFF4B2890
RDI=00000000003715D0 RSI=0000000000378490 RAX=0000000000000000 RBX=00000000FFFFFFFF
RCX=0000000000389E00 RDX=0000000003DB18E8 R8=0000000000000001 R9=0000000000000001
R10=0000000001594EF0 R11=0000000003D50540 R12=0000000003D50540 R13=0000000000000001
R14=0000000003DB18E8 R15=0000000000389E00
RIP=000007FFFF2D90C2 RSP=000000000023F218 RBP=0000000000000001 GS=002B
FS=0053 ES=002B DS=002B
XMM0 000000000000027f (f: 639.000000, d: 3.157079e-321)
XMM1 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM2 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM3 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM4 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM5 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM6 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM7 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM8 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM9 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM10 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM11 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM12 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM13 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM14 0000000000000000 (f: 0.000000, d: 0.000000e+000)
XMM15 0000000000000000 (f: 0.000000, d: 0.000000e+000)
Module=C:\test\sdk\jre\bin\default\j9trc26.dll
Module_base_address=000007FFFF2D0000 Offset_in_DLL=00000000000090c2
Target=2_60_20101120_069090 (Windows Server 2008 R2 6.1 build 7600)
CPU=amd64 (4 logical CPUs) (0x1bfefb000 RAM)
----------- Stack Backtrace -----------
---------------------------------------
JVMDUMP006I Processing dump event "gpf", detail "" - please wait.
JVMDUMP032I JVM requested System dump using 'C:\Users\Administrator\core.20101122.
101637.7148.0001.dmp' in response to an event
JVMDUMP010I System dump written to C:\Users\Administrator\core.20101122.101637.
7148.0001.dmp
JVMDUMP032I JVM requested Java dump using 'C:\Users\Administrator\javacore.
20101122.101637.7148.0002.txt' in response to an event
JVMDUMP010I Java dump written to C:\Users\Administrator\javacore.20101122.101637.
7148.0002.txt
JVMDUMP032I JVM requested Snap dump using 'C:\Users\Administrator\Snap.20101122.
101637.7148.0003.trc' in response to an event
JVMDUMP010I Snap dump written to C:\Users\Administrator\Snap.20101122.101637.7148.
0003.trc
JVMDUMP013I Processed dump event "gpf", detail "".

In this example, the JVM has generated the dump in the file D:\core.20040817.131302.2168.dmp.

The JVM attempts to generate the system dump file in one of the following directories (listed in order of precedence):

Any directory specified on the command line, for example by using the -Xdump:<agent>:file or -Xdump:directory options.
The directory pointed to by environment variable IBM_COREDIR.
The current directory.
The directory pointed to by the environment variable TMPDIR.
The C:\Temp directory

Use -Xdump:what to find the current naming convention of all dump files. Use -Xdump:help to learn how to change these settings.

You might want to keep system dumps more private by setting the environment variable IBM_COREDIR, if you are concerned about passwords and other security details that are contained in a system dump.