Summary of Tools in This Release

This appendix presents a summary of tools available in the current release of the JDK, as well as the changes since the previous release.

D.1 Troubleshooting Tools Available in JDK 7

This section lists the troubleshooting tools available by platform: Unix (Solaris OS and Linux) and Windows.

D.1.1 Solaris OS and Linux

All the JDK troubleshooting tools that are described in this document are available in JDK 7 on both Solaris OS and Linux.

D.1.2 Windows Operating System

The following JDK troubleshooting tools are also available in JDK 7 on the Windows operating system.

• HPROF profiler

• JConsole utility

• jdb utility

• jhat utility

• jinfo utility

• jmap utility

• jps utility (not currently available on Windows 98 or Windows ME)

• jrunscript utility

• jstack utility

• jstat utility (not currently available on Windows 98 or Windows ME)

• jstatd daemon (not currently available on Windows 98 or Windows ME)

• visualgc tool (not currently available on Windows 98 or Windows ME)

D.2 Changes to Troubleshooting Tools in JDK 7

This is a list of changes to the JDK troubleshooting tools and options from JDK 1.5 to JDK 7.

• The Java VisualVM tool is included in JDK releases starting with release 6 update 7.

• The Heap Analysis Tool (HAT) has been replaced by the new jhat command–line tool. This new tool has the same functionality as HAT, with the following additional enhancements:

  • jhat can parse incomplete and truncated heap dumps.

  • jhat can read heap dumps generated on 64–bit systems.

  • jhat supports Object Query Language (OQL), with which you can create your own queries on the heap dump.

• The JConsole tool has the following changes.

  • A new user interface (button) is provided for deadlock detection, including java.util.concurrent locks.

  • The Connection dialog is new.

  • The Overview tab is new.

  • You no longer need to specify the -Dcom.sun.management.jmxremote command-line option when starting the application to be monitored.

  • You can connect to a VM using the attach mechanism.

  • You can pass a flag on the command line to the VM that is running JConsole.

  • The com.sun.management.HotSpotDiagnostic MBean property is new. In the MBean tab, you can use this property to dump heap, get and set VM options, and change management options dynamically.

• The jdb tool has the following changes:

  • Shows return values in method and exit traces.

  • Trace method entry/exit without stopping.

  • The JPDA ProcessAttachingConnector is new.

• The jinfo tool has the following changes:

  • The new jinfo -flag option allows you to dynamically set, unset, and change the values of certain Java VM flags for a specified Java process.

  • The jinfo command is new to Windows, but only the option jinfo -flag pid.

• The jmap command has the following changes:

  • The jmap -finalizerinfo option is new. With this option, the command prints information on objects awaiting finalization.

  • The jmap -permstat option has been updated to print also the number and size of internalized String instances.

  • The jmap -dump:format=b,file=filename option is new. With this option, jmap obtains a heap dump from a running process or from a core file and writes it in binary HPROF format to a specified file. This file can then be analyzed with the jhat tool.

  • The jmap -F option is new and is for Solaris OS and Linux only. This option forces the use of the Serviceability Agent in case the process does not respond.

  • The jmap -J option is new and is for Solaris OS and Linux only. This option passes flags to the VM on which jmap is running.

  • The live suboption is new for the histo option. With this suboption only live objects are counted.

  • The jmap command is new to Windows, but only the jmap -dump:dump-options pid option and the jmap -histo[:live] pid option.

• The jrunscript tool is new.

• The jstack command has the following changes:

  • The jstack pid option has been changed to work like remote Ctrl-Break, that is, the output of the thread dump is slightly different, and there is more information on deadlocks and JNI Global References.

  • The jstack -F option is new and is for Solaris OS and Linux only. This option forces a thread dump in case the VM is hung.

  • The jstack -l option is new. This option prints information about ownable synchronizers (locks) in the heap.

  • The jstack command is new to Windows, but only the jstack pid option and the jstack -l pid option.

• The -XX:OnOutOfMemoryError=string option allows you to specify a command or script to be run when an OutOfMemoryError is first thrown. This is useful for data capture, for example, with jmap.

• The -XX:+HeapDumpOnOutOfMemoryError command-line option is new as of JDK release 5 update 7. If this option is set and the VM detects a native out–of–memory error, a heap dump is generated. See B.1.2 -XX:+HeapDumpOnOutOfMemoryError Option.

• Other new environment variables to help in troubleshooting out-of-memory errors are the following:

  • -XX:HeapDumpPath=pathname

  • -XX:SegmentedHeapDumpThreshold=threshold

  • -XX:HeapDumpSegmentSize=size

• The fatal error log has the following changes:

  • You now have the ability to specify a location for the fatal error log. See C.1 Location of Fatal Error Log.

  • There is now a URL at the beginning of fatal error log for reporting incidents. See C.3 Header Format.

• The VM now contains two built-in DTrace probe providers: hotspot and hotspot_jni. (Solaris 10 OS only)

• The fastdebug builds can be useful for testing, diagnosing, and isolating problems. However, they should not be used in production environments.

• The Ctrl-Break handler has the following changes:

  • Ctrl-Break now shows the thread state.

  • Ctrl-Break now shows the sizes of the heap areas.

  • With -XX:+PrintConcurrentLocks, Ctrl-Break will also print the list of concurrent locks owned by each thread, as well as detect deadlocks involving both monitor locks and concurrent locks.

• The HPROF format=b option now includes primitive type instance fields and primitive array content in heap dumps.

• When the java.lang.OutOfMemoryError error is thrown, a stack trace is now printed also. In addition, when the specific message indicates that the system is almost out of swap space (Out of swap space?), a fatal error log is now generated.