JVM Troubleshooting

Java Platform, Standard Edition Troubleshooting Guide: https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/toc.html

JVM - jstat

Monitors Java Virtual Machine (JVM) statistics. This command is experimental and unsupported.

jstat [ generalOption | outputOptions vmid [ interval[s|ms] [ count ] ]
//vmid: [protocol:][//]lvmid[@hostname[:port]/servername]

refer: https://docs.oracle.com/javase/8/docs/technotes/tools/windows/jstat.html

JVM - jcmd

The jcmd utility is used to send diagnostic command requests to the JVM, where these requests are useful for controlling Java Flight Recordings, troubleshoot, and diagnose JVM and Java Applications. It must be used on the same machine where the JVM is running, and have the same effective user and group identifiers that were used to launch the JVM.
 Sample
 jcmd
 jcmd <process id/main class> PerfCounter.print
 jcmd 2125 help //2125 is the pid
 jcmd 2125 GC.heap_dump filename=Myheapdump
 jcmd 2125 VM.uptime
 jcmd <process id/main class> VM.system_properties
 jcmd <process id/main class> VM.flags
 jcmd MyProgram help Thread.print
 jcmd <process id/main class> Thread.print
 jcmd <process id/main class> [options]
 jcmd 7060 JFR.start name=MyRecording settings=profile delay=20s duration=2m filename=C:\TEMP\myrecording.jfr
 jcmd 7060 JFR.check
 jcmd 7060 JFR.stop
jcmd man page: https://docs.oracle.com/javase/8/docs/technotes/tools/windows/jcmd.html
Useful Commands for jcmd Utility: https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/tooldescr006.html#BABEJDGE
Troubleshoot with jcmd Utility: https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/tooldescr006.html#BABFFIFA

JVM - jps

Lists the instrumented Java Virtual Machines (JVMs of HotSpot) on the target system. This command is experimental and unsupported.
 A jstatd process is assumed to be running on the target host.
 The jps command uses the Java launcher to find the class name and arguments passed to the main method. If the target JVM is started with a custom launcher, then the class or JAR file name and the arguments to the main method are not available. In this case, the jps command outputs the string Unknown for the class name or JAR file name and for the arguments to the main method.
 The command only lists the JVMs for which the principle has access rights as determined by operating system-specific access control mechanisms.
 Sample
 jps
 jps –l remote.domain
 jps –m remote.domain:2002 (see jstatd –n)

Refer: https://docs.oracle.com/javase/8/docs/technotes/tools/windows/jps.html

core dump 或者 crash dump

core dump:A core dump or a crash dump is a memory snapshot of a running process.

A core dump can be automatically created by the operating system when a fatal or unhandled error (for example, signal or system exception) occurs.
or can be forced by means of system-provided command-line utilities.
kill -6 on Linux or Solaris systems 将会强制产生一个core 文件,即使程序无响应。
更多如何获得 参看 这里

IBM JVM(J9) 的javacore 文件和一般进程的core dump 不是一回事。
IBM JVM (J9) java core file: http://www-01.ibm.com/support/docview.wss?uid=swg21393547