IBM User Guide for Java V7 on Windows > Troubleshooting and support > Using diagnostic tools > Using system dumps and the dump viewer
Using the dump viewer
System dumps are produced in a platform-specific binary format, typically as a raw memory image of the process that was running at the time the dump was initiated. The SDK dump viewer allows you to navigate around the dump, and obtain information in a readable form, with symbolic (source code) data where possible.
You can view Java™ information (for example, threads and objects on the heap) and native information (for example, native stacks, libraries, and raw memory locations). You can run the dump viewer on one platform to work with dumps from another platform. For example, you can look at Linux dumps on a Windows platform.
Dump viewer: jdmpview
The dump viewer is a tool that allows you to examine the contents of system dumps produced from the JVM. The dump viewer requires metadata created by the jextract utility, if the system dump was generated by a version of the IBM J9 virtual machine before V2.6. To check the version of a JVM, use the java -version command and examine the output. The dump viewer allows you to view both Java and native information from the time the dump was produced.jdmpview is in the directory sdk/bin.
To start jdmpview, from a shell prompt, enter:
jdmpview -zip <zip file>
or
jdmpview -core <core file> [-xml <xml file>]
The jdmpview tool accepts these parameters:
- -core <core file>
- Specify a dump file.
-notemp
- By default, when you specify a file by using the -zip option,
the contents are extracted to a temporary directory before processing.
Use the -notemp option to prevent this extraction
step, and run all subsequent commands in memory.
- -xml <xml file>
- Specify a metadata file. jdmpview guesses the name of the XML file if the -xml option is not present. This option is not required for core files generated from an IBM J9 2.6 virtual machine.
- -zip <zip file>
- Specify a compressed file containing the core file and associated XML file (produced by jextract).
Note: The -core and -xml options can be used with the -zip option to specify the core and XML files in the compressed file. Without the -core or -xml options, jdmpview shows
multiple contexts, one for each source file that it identified in the compressed file. For more information, see Support for compressed files.
After jdmpview processes the arguments with which it was started, it shows this message:
For a list of commands, type "help"; for how to use "help", type "help help" >When you see this message, you can start using commands.
When jdmpview is used with the -zip option, temporary disk space
is required to uncompress the dump files from the compressed file. jdmpview uses
the system temporary directory, /tmp on AIX, Linux,
or zOS, or a user-specific temporary directory in C:\Documents and Settings\ on Windows. An alternative temporary directory can be specified using the Java system property java.io.tmpdir. jdmpview shows
an error message if insufficient disk space is available in the temporary
directory. Use the -notemp option to prevent jdmpview from creating these temporary
files. The temporary files are deleted when jdmpview exits
or when you enter the close command on the command
line.
You can significantly improve the performance of jdmpview against
large dumps by ensuring that your system has enough memory available
to avoid paging. On large dumps (that is, ones with large numbers
of objects on the heap), you might have to run jdmpview using
the -Xmx option to increase the maximum heap
available. You might also have
to increase the maximum heap size if you use the -notemp option,
especially if you are analyzing a large heap, because this option specifies that all analysis is done in memory.
jdmpview -J-Xmx<n> -zip <zip file>To pass command-line arguments to the JVM, you must prefix them with -J.
- Support for compressed files
When you run the jdmpview tool on a compressed file, the tool detects and shows all system dump, Java dump, and heap dump files within the compressed file. Because of this behavior, more than one context might be displayed when you start jdmpview. - Using jextract
Use the jextract utility to process system dumps. - Problems to tackle with the dump viewer
Dumps of JVM processes can arise either when you use the -Xdump option on the command line or when the JVM is not in control (such as user-initiated dumps). - Using the dump viewer in batch mode
For long running or routine jobs, jdmpview can be used in batch mode. - Commands available in jdmpview
jdmpview is an interactive, command-line tool to explore the information from a JVM system dump and perform various analysis functions. - Example session
This example session illustrates a selection of the commands available and their use. - jdmpview commands quick reference
A short list of the commands you use with jdmpview.
Parent: Using system dumps and the dump viewer
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