Description: This section describes the diagnostic commands of JDK Mission Control.

Go to primary content

| Previous | Next |

# Types of Diagnostic Commands

This section describes the diagnostic commands of JDK Mission Control.

Standard Commands

Standard commands are denoted by a green icon with the letter `i` in a circle. They provide general diagnostic information.

- `JFR.check`

  Prints the status of the running JFR recordings.

- `JFR.dump`

  Dumps the current data in the specified JFR recording to a recording file.

- `JFR.stop`

  Stops the specified JFR recording.

- `VM.check_commercial_features`

  Prints the status of commercial features.

- `VM.command_line`

  Prints the command line arguments that were used to start the JVM.

- `VM.flags`

  Prints the JVM flags and their current values.

- `VM.system_properties`

  Prints the system properties and their current values.

- `VM.unlock_commercial_features`

  Unlocks the commercial features.

- `VM.uptime`

  Prints the JVM uptime since it was launched.

- `VM.version`

  Prints the JVM version information.

- `help`

  Prints a list of available commands, help information for the specified command, or help for all commands.

Advanced Commands

Advanced commands are denoted by a yellow icon with an exclamation mark (!) in a triangle. They require more resources, can impact JVM performance, but provide more information.

- `GC.run`

  Calls the java.lang.System.gc() method that runs the garbage collector. Garbage collection performance depends on the size and contents of the Java heap.

- `GC.run_finalization`

  Calls the java.lang.System.runFinalization() method that runs the finalization methods of all objects pending finalization.

- `JFR.start`

  Starts a JFR recording.

- `Thread.print`

  Prints stack traces for all threads.

- `VM.native_memory`

  Prints native memory usage.

Internal Commands

Internal commands are denoted by a red icon with an exclamation mark (!) in an upside-down triangle. These provide very detailed diagnostic information, but greatly impact the JVM performance. Their impact depends on the size and contents of the Java heap.

- `GC.class_histogram`

  Prints detailed Java heap usage statistics.

- `GC.class_stats`

  Prints statistics about the Java class metadata. This command requires the `-XX:+UnlockDiagnosticVMOptions` to be enabled when starting the JVM.

- `GC.heap_dump`

  Generate a dump of the Java heap to an `HPROF` file.

Copyright © 2018, Oracle and/or its affiliates. All rights reserved. | Previous | Next |