1JCMD(1) JDK Commands JCMD(1)
2
6 jcmd - send diagnostic command requests to a running Java Virtual Ma‐
7 chine (JVM)
8
10 jcmd [pid | main-class] command... | PerfCounter.print | -f filename
11 jcmd [-l]
13 jcmd -h
15 pid When used, the jcmd utility sends the diagnostic command request
17 to the process ID for the Java process.
18 main-class
20 When used, the jcmd utility sends the diagnostic command request
21 to all Java processes with the specified name of the main class.
22 command
24 The command must be a valid jcmd command for the selected JVM.
25 The list of available commands for jcmd is obtained by running
26 the help command (jcmd pid help) where pid is the process ID for
27 the running Java process. If the pid is 0, commands will be
28 sent to all Java processes. The main class argument will be
29 used to match, either partially or fully, the class used to
30 start Java. If no options are given, it lists the running Java
31 process identifiers with the main class and command-line argu‐
32 ments that were used to launch the process (the same as using
33 -l).
34 Perfcounter.print
36 Prints the performance counters exposed by the specified Java
37 process.
38 -f filename
40 Reads and executes commands from a specified file, filename.
41 -l Displays the list of Java Virtual Machine process identifiers
43 that are not running in a separate docker process along with the
44 main class and command-line arguments that were used to launch
45 the process. If the JVM is in a docker process, you must use
46 tools such as ps to look up the PID.
47 Note:
49 Using jcmd without arguments is the same as using jcmd -l.
51 -h Displays the jcmd utility's command-line help.
53
55 The jcmd utility is used to send diagnostic command requests to the
56 JVM. It must be used on the same machine on which the JVM is running,
57 and have the same effective user and group identifiers that were used
58 to launch the JVM. Each diagnostic command has its own set of argu‐
59 ments. To display the description, syntax, and a list of available ar‐
60 guments for a diagnostic command, use the name of the command as the
61 argument. For example:
62 jcmd pid help command
64 If arguments contain spaces, then you must surround them with single or
66 double quotation marks (' or "). In addition, you must escape single
67 or double quotation marks with a backslash (\) to prevent the operating
68 system shell from processing quotation marks. Alternatively, you can
69 surround these arguments with single quotation marks and then with dou‐
70 ble quotation marks (or with double quotation marks and then with sin‐
71 gle quotation marks).
72 If you specify the process identifier (pid) or the main class
74 (main-class) as the first argument, then the jcmd utility sends the di‐
75 agnostic command request to the Java process with the specified identi‐
76 fier or to all Java processes with the specified name of the main
77 class. You can also send the diagnostic command request to all avail‐
78 able Java processes by specifying 0 as the process identifier.
79
81 The command must be a valid jcmd diagnostic command for the selected
82 JVM. The list of available commands for jcmd is obtained by running
83 the help command (jcmd pid help) where pid is the process ID for a run‐
84 ning Java process. If the pid is 0, commands will be sent to all Java
85 processes. The main class argument will be used to match, either par‐
86 tially or fully, the class used to start Java. If no options are giv‐
87 en, it lists the running Java process identifiers that are not in sepa‐
88 rate docker processes along with the main class and command-line argu‐
89 ments that were used to launch the process (the same as using -l).
90 The following commands are available:
92 help [options] [arguments]
94 For more information about a specific command.
95 arguments:
97 • command name: The name of the command for which we want help
99 (STRING, no default value)
100 Note:
102 The following options must be specified using either key or
104 key=value syntax.
105 options:
107 • -all: (Optional) Show help for all commands (BOOLEAN, false) .
109 Compiler.codecache
111 Prints code cache layout and bounds.
112 Impact: Low
114 Permission: java.lang.management.ManagementPermission(monitor)
116 Compiler.codelist
118 Prints all compiled methods in code cache that are alive.
119 Impact: Medium
121 Permission: java.lang.management.ManagementPermission(monitor)
123 Compiler.perfmap (Linux only)
125 Write map file for Linux perf tool.
126 Impact: Low
128 Permission: java.lang.management.ManagementPermission(monitor)
130 Compiler.queue
132 Prints methods queued for compilation.
133 Impact: Low
135 Permission: java.lang.management.ManagementPermission(monitor)
137 Compiler.directives_add *filename* *arguments*
139 Adds compiler directives from a file.
140 Impact: Low
142 Permission: java.lang.management.ManagementPermission(monitor)
144 arguments:
146 filename: The name of the directives file (STRING, no default
148 value)
149 Compiler.directives_clear
151 Remove all compiler directives.
152 Impact: Low
154 Permission: java.lang.management.ManagementPermission(monitor)
156 Compiler.directives_print
158 Prints all active compiler directives.
159 Impact: Low
161 Permission: java.lang.management.ManagementPermission(monitor)
163 Compiler.directives_remove
165 Remove latest added compiler directive.
166 Impact: Low
168 Permission: java.lang.management.ManagementPermission(monitor)
170 GC.class_histogram [options]
172 Provides statistics about the Java heap usage.
173 Impact: High --- depends on Java heap size and content.
175 Permission: java.lang.management.ManagementPermission(monitor)
177 Note:
179 The options must be specified using either key or key=value syn‐
181 tax.
182 options:
184 • -all: (Optional) Inspects all objects, including unreachable
186 objects (BOOLEAN, false)
187 • -parallel: (Optional) Number of parallel threads to use for
189 heap inspection. 0 (the default) means let the VM determine
190 the number of threads to use. 1 means use one thread (disable
191 parallelism). For any other value the VM will try to use the
192 specified number of threads, but might use fewer. (INT, 0)
193 GC.finalizer_info
195 Provides information about the Java finalization queue.
196 Impact: Medium
198 Permission: java.lang.management.ManagementPermission(monitor)
200 GC.heap_dump [options] [arguments]
202 Generates a HPROF format dump of the Java heap.
203 Impact: High --- depends on the Java heap size and content. Re‐
205 quest a full GC unless the -all option is specified.
206 Permission: java.lang.management.ManagementPermission(monitor)
208 Note:
210 The following options must be specified using either key or
212 key=value syntax.
213 options:
215 • -all: (Optional) Dump all objects, including unreachable ob‐
217 jects (BOOLEAN, false)
218 • -gz: (Optional) If specified, the heap dump is written in
220 gzipped format using the given compression level. 1 (recom‐
221 mended) is the fastest, 9 the strongest compression. (INT, 1)
222 • -overwrite: (Optional) If specified, the dump file will be
224 overwritten if it exists (BOOLEAN, false)
225 arguments:
227 • filename: The name of the dump file (STRING, no default value)
229 GC.heap_info
231 Provides generic Java heap information.
232 Impact: Medium
234 Permission: java.lang.management.ManagementPermission(monitor)
236 GC.run Calls java.lang.System.gc().
238 Impact: Medium --- depends on the Java heap size and content.
240 GC.run_finalization
242 Calls java.lang.System.runFinalization().
243 Impact: Medium --- depends on the Java content.
245 JFR.check [options]
247 Show information about a running flight recording
248 Impact: Low
250 Note:
252 The options must be specified using either key or key=value syn‐
254 tax. If no parameters are entered, information for all active
255 recordings is shown.
256 options:
258 • name: (Optional) Name of the flight recording. (STRING, no
260 default value)
261 • verbose: (Optional) Flag for printing the event settings for
263 the recording (BOOLEAN, false)
264 JFR.configure [options]
266 Set the parameters for a flight recording
267 Impact: Low
269 Note:
271 The options must be specified using either key or key=value syn‐
273 tax. If no parameters are entered, the current settings are
274 displayed.
275 options:
277 • globalbuffercount: (Optional) Number of global buffers. This
279 option is a legacy option: change the memorysize parameter to
280 alter the number of global buffers. This value cannot be
281 changed once JFR has been initialized. (STRING, default de‐
282 termined by the value for memorysize)
283 • globalbuffersize: (Optional) Size of the global buffers, in
285 bytes. This option is a legacy option: change the memorysize
286 parameter to alter the size of the global buffers. This value
287 cannot be changed once JFR has been initialized. (STRING, de‐
288 fault determined by the value for memorysize)
289 • maxchunksize: (Optional) Maximum size of an individual data
291 chunk in bytes if one of the following suffixes is not used:
292 'm' or 'M' for megabytes OR 'g' or 'G' for gigabytes. This
293 value cannot be changed once JFR has been initialized.
294 (STRING, 12M)
295 • memorysize: (Optional) Overall memory size, in bytes if one of
297 the following suffixes is not used: 'm' or 'M' for megabytes
298 OR 'g' or 'G' for gigabytes. This value cannot be changed
299 once JFR has been initialized. (STRING, 10M)
300 • repositorypath: (Optional) Path to the location where record‐
302 ings are stored until they are written to a permanent file.
303 (STRING, The default location is the temporary directory for
304 the operating system. On Linux operating systems, the tempo‐
305 rary directory is /tmp. On Windwows, the temporary directory
306 is specified by the TMP environment variable.)
307 • stackdepth: (Optional) Stack depth for stack traces. Setting
309 this value greater than the default of 64 may cause a perfor‐
310 mance degradation. This value cannot be changed once JFR has
311 been initialized. (LONG, 64)
312 • thread_buffer_size: (Optional) Local buffer size for each
314 thread in bytes if one of the following suffixes is not used:
315 'k' or 'K' for kilobytes or 'm' or 'M' for megabytes. Over‐
316 riding this parameter could reduce performance and is not rec‐
317 ommended. This value cannot be changed once JFR has been ini‐
318 tialized. (STRING, 8k)
319 • samplethreads: (Optional) Flag for activating thread sampling.
321 (BOOLEAN, true)
322 JFR.dump [options]
324 Write data to a file while a flight recording is running
325 Impact: Low
327 Note:
329 The options must be specified using either key or key=value syn‐
331 tax. No options are required. The recording continues to run
332 after the data is written.
333 options:
335 • begin: (Optional) Specify the time from which recording data
337 will be included in the dump file. The format is specified as
338 local time. (STRING, no default value)
339 • end: (Optional) Specify the time to which recording data will
341 be included in the dump file. The format is specified as lo‐
342 cal time. (STRING, no default value)
343 Note: For both begin and end, the time must be in a format
345 that can be read by java.time.LocalTime::parse(STRING), ja‐
346 va.time.LocalDateTime::parse(STRING) or java.time.In‐
347 stant::parse(STRING). For example, "13:20:15",
348 "2020-03-17T09:00:00" or "2020-03-17T09:00:00Z".
349 Note: begin and end times correspond to the timestamps found
351 within the recorded information in the flight recording data.
352 Another option is to use a time relative to the current time
354 that is specified by a negative integer followed by "s", "m"
355 or "h". For example, "-12h", "-15m" or "-30s"
356 • filename: (Optional) Name of the file to which the flight
358 recording data is dumped. If no filename is given, a filename
359 is generated from the PID and the current date. The filename
360 may also be a directory in which case, the filename is gener‐
361 ated from the PID and the current date in the specified direc‐
362 tory. (STRING, no default value)
363 • maxage: (Optional) Length of time for dumping the flight
365 recording data to a file. (INTEGER followed by 's' for sec‐
366 onds 'm' for minutes or 'h' for hours, no default value)
367 • maxsize: (Optional) Maximum size for the amount of data to
369 dump from a flight recording in bytes if one of the following
370 suffixes is not used: 'm' or 'M' for megabytes OR 'g' or 'G'
371 for gigabytes. (STRING, no default value)
372 • name: (Optional) Name of the recording. If no name is given,
374 data from all recordings is dumped. (STRING, no default val‐
375 ue)
376 • path-to-gc-root: (Optional) Flag for saving the path to
378 garbage collection (GC) roots at the time the recording data
379 is dumped. The path information is useful for finding memory
380 leaks but collecting it can cause the application to pause for
381 a short period of time. Turn on this flag only when you have
382 an application that you suspect has a memory leak. (BOOLEAN,
383 false)
384 JFR.start [options]
386 Start a flight recording
387 Impact: Low
389 Note:
391 The options must be specified using either key or key=value syn‐
393 tax. If no parameters are entered, then a recording is started
394 with default values.
395 options:
397 • delay: (Optional) Length of time to wait before starting to
399 record (INTEGER followed by 's' for seconds 'm' for minutes or
400 'h' for hours, 0s)
401 • disk: (Optional) Flag for also writing the data to disk while
403 recording (BOOLEAN, true)
404 • dumponexit: (Optional) Flag for writing the recording to disk
406 when the Java Virtual Machine (JVM) shuts down. If set to
407 'true' and no value is given for filename, the recording is
408 written to a file in the directory where the process was
409 started. The file name is a system-generated name that con‐
410 tains the process ID, the recording ID and the current time
411 stamp. (For example: id-1-2019_12_12_10_41.jfr) (BOOLEAN,
412 false)
413 • duration: (Optional) Length of time to record. Note that 0s
415 means forever (INTEGER followed by 's' for seconds 'm' for
416 minutes or 'h' for hours, 0s)
417 • filename: (Optional) Name of the file to which the flight
419 recording data is written when the recording is stopped. If
420 no filename is given, a filename is generated from the PID and
421 the current date and is placed in the directory where the
422 process was started. The filename may also be a directory in
423 which case, the filename is generated from the PID and the
424 current date in the specified directory. (STRING, no default
425 value)
426 • maxage: (Optional) Maximum time to keep the recorded data on
428 disk. This parameter is valid only when the disk parameter is
429 set to true. Note 0s means forever. (INTEGER followed by 's'
430 for seconds 'm' for minutes or 'h' for hours, 0s)
431 • maxsize: (Optional) Maximum size of the data to keep on disk
433 in bytes if one of the following suffixes is not used: 'm' or
434 'M' for megabytes OR 'g' or 'G' for gigabytes. This parameter
435 is valid only when the disk parameter is set to 'true'. The
436 value must not be less than the value for the maxchunksize pa‐
437 rameter set with the JFR.configure command. (STRING, 0 (no
438 maximum size))
439 • name: (Optional) Name of the recording. If no name is provid‐
441 ed, a name is generated. Make note of the generated name that
442 is shown in the response to the command so that you can use it
443 with other commands. (STRING, system-generated default name)
444 • path-to-gc-root: (Optional) Flag for saving the path to
446 garbage collection (GC) roots at the end of a recording. The
447 path information is useful for finding memory leaks but col‐
448 lecting it is time consuming. Turn on this flag only when you
449 have an application that you suspect has a memory leak. If
450 the settings parameter is set to 'profile', then the informa‐
451 tion collected includes the stack trace from where the poten‐
452 tial leaking object was allocated. (BOOLEAN, false)
453 • settings: (Optional) Name of the settings file that identifies
455 which events to record. To specify more than one file, sepa‐
456 rate the names with a comma (','). Include the path if the
457 file is not in JAVA-HOME/lib/jfr. The following profiles are
458 included with the JDK in the JAVA-HOME/lib/jfr directory: 'de‐
459 fault.jfc': collects a predefined set of information with low
460 overhead, so it has minimal impact on performance and can be
461 used with recordings that run continuously; 'profile.jfc':
462 Provides more data than the 'default.jfc' profile, but with
463 more overhead and impact on performance. Use this configura‐
464 tion for short periods of time when more information is need‐
465 ed. Use none to start a recording without a predefined con‐
466 figuration file. (STRING, JAVA-HOME/lib/jfr/default.jfc)
467 Event settings and .jfc options can be specified using the fol‐
469 lowing syntax:
470 • option: (Optional) Specifies the option value to modify. To
472 list available options, use the JAVA_HOME/bin/jfr tool.
473 • event-setting: (Optional) Specifies the event setting value to
475 modify. Use the form: <event-name>#<setting-name>=<value> To
476 add a new event setting, prefix the event name with '+'.
477 You can specify values for multiple event settings and .jfc op‐
479 tions by separating them with a whitespace. In case of a con‐
480 flict between a parameter and a .jfc option, the parameter will
481 take precedence. The whitespace delimiter can be omitted for
482 timespan values, i.e. 20ms. For more information about the
483 settings syntax, see Javadoc of the jdk.jfr package.
484 JFR.stop [options]
486 Stop a flight recording
487 Impact: Low
489 Note:
491 The options must be specified using either key or key=value syn‐
493 tax. If no parameters are entered, then no recording is
494 stopped.
495 options:
497 • filename: (Optional) Name of the file to which the recording
499 is written when the recording is stopped. If no path is pro‐
500 vided, the data from the recording is discarded. (STRING, no
501 default value)
502 • name: (Optional) Name of the recording (STRING, no default
504 value)
505 JVMTI.agent_load [arguments]
507 Loads JVMTI native agent.
508 Impact: Low
510 Permission: java.lang.management.ManagementPermission(control)
512 arguments:
514 • library path: Absolute path of the JVMTI agent to load.
516 (STRING, no default value)
517 • agent option: (Optional) Option string to pass the agent.
519 (STRING, no default value)
520 JVMTI.data_dump
522 Signals the JVM to do a data-dump request for JVMTI.
523 Impact: High
525 Permission: java.lang.management.ManagementPermission(monitor)
527 ManagementAgent.start [options]
529 Starts remote management agent.
530 Impact: Low --- no impact
532 Note:
534 The following options must be specified using either key or
536 key=value syntax.
537 options:
539 • config.file: (Optional) Sets com.sun.management.config.file
541 (STRING, no default value)
542 • jmxremote.host: (Optional) Sets com.sun.management.jmxre‐
544 mote.host (STRING, no default value)
545 • jmxremote.port: (Optional) Sets com.sun.management.jmxre‐
547 mote.port (STRING, no default value)
548 • jmxremote.rmi.port: (Optional) Sets com.sun.management.jmxre‐
550 mote.rmi.port (STRING, no default value)
551 • jmxremote.ssl: (Optional) Sets com.sun.management.jmxre‐
553 mote.ssl (STRING, no default value)
554 • jmxremote.registry.ssl: (Optional) Sets com.sun.manage‐
556 ment.jmxremote.registry.ssl (STRING, no default value)
557 • jmxremote.authenticate: (Optional) Sets com.sun.manage‐
559 ment.jmxremote.authenticate (STRING, no default value)
560 • jmxremote.password.file: (Optional) Sets com.sun.manage‐
562 ment.jmxremote.password.file (STRING, no default value)
563 • jmxremote.access.file: (Optional) Sets com.sun.manage‐
565 ment.jmxremote.acce ss.file (STRING, no default value)
566 • jmxremote.login.config: (Optional) Sets com.sun.manage‐
568 ment.jmxremote.log in.config (STRING, no default value)
569 • jmxremote.ssl.enabled.cipher.suites: (Optional) Sets
571 com.sun.management.
572 • jmxremote.ssl.enabled.cipher.suite: (STRING, no default value)
574 • jmxremote.ssl.enabled.protocols: (Optional) Sets com.sun.man‐
576 agement.jmxr emote.ssl.enabled.protocols (STRING, no default
577 value)
578 • jmxremote.ssl.need.client.auth: (Optional) Sets com.sun.man‐
580 agement.jmxre mote.need.client.auth (STRING, no default value)
581 • jmxremote.ssl.config.file: (Optional) Sets com.sun.manage‐
583 ment.jmxremote. ssl_config_file (STRING, no default value)
584 • jmxremote.autodiscovery: (Optional) Sets com.sun.manage‐
586 ment.jmxremote.au todiscovery (STRING, no default value)
587 • jdp.port: (Optional) Sets com.sun.management.jdp.port (INT, no
589 default value)
590 • jdp.address: (Optional) Sets com.sun.management.jdp.address
592 (STRING, no default value)
593 • jdp.source_addr: (Optional) Sets com.sun.manage‐
595 ment.jdp.source_addr (STRING, no default value)
596 • jdp.ttl: (Optional) Sets com.sun.management.jdp.ttl (INT, no
598 default value)
599 • jdp.pause: (Optional) Sets com.sun.management.jdp.pause (INT,
601 no default value)
602 • jdp.name: (Optional) Sets com.sun.management.jdp.name (STRING,
604 no default value)
605 ManagementAgent.start_local
607 Starts the local management agent.
608 Impact: Low --- no impact
610 ManagementAgent.status
612 Print the management agent status.
613 Impact: Low --- no impact
615 Permission: java.lang.management.ManagementPermission(monitor)
617 ManagementAgent.stop
619 Stops the remote management agent.
620 Impact: Low --- no impact
622 System.trim_native_heap (Linux only)
624 Attempts to free up memory by trimming the C-heap.
625 Impact: Low
627 Permission: java.lang.management.ManagementPermission(control)
629 Thread.print [options]
631 Prints all threads with stacktraces.
632 Impact: Medium --- depends on the number of threads.
634 Permission: java.lang.management.ManagementPermission(monitor)
636 Note:
638 The following options must be specified using either key or
640 key=value syntax.
641 options:
643 • -e: (Optional) Print extended thread information (BOOLEAN,
645 false)
646 • -l: (Optional) Prints java.util.concurrent locks (BOOLEAN,
648 false)
649 VM.cds [arguments]
651 Dumps a static or dynamic shared archive that includes all cur‐
652 rently loaded classes.
653 Impact: Medium --- pause time depends on number of loaded class‐
655 es
656 Permission: java.lang.management.ManagementPermission(monitor)
658 arguments:
660 • subcmd: must be either static_dump or dynamic_dump (STRING, no
662 default value)
663 • filename: (Optional) Name of the shared archive to be dumped
665 (STRING, no default value)
666 If filename is not specified, a default file name is chosen us‐
668 ing the pid of the target JVM process. For example, ja‐
669 va_pid1234_static.jsa, java_pid5678_dynamic.jsa, etc.
670 If filename is not specified as an absolute path, the archive
672 file is created in a directory relative to the current directory
673 of the target JVM process.
674 If dynamic_dump is specified, the target JVM must be started
676 with the JVM option -XX:+RecordDynamicDumpInfo.
677 VM.classloaders [options]
679 Prints classloader hierarchy.
680 Impact: Medium --- Depends on number of class loaders and class‐
682 es loaded.
683 Permission: java.lang.management.ManagementPermission(monitor)
685 The following options must be specified using either key or
687 key=value syntax.
688 options:
690 • show-classes: (Optional) Print loaded classes. (BOOLEAN,
692 false)
693 • verbose: (Optional) Print detailed information. (BOOLEAN,
695 false)
696 • fold: (Optional) Show loaders of the same name and class as
698 one. (BOOLEAN, true)
699 VM.classloader_stats
701 Prints statistics about all ClassLoaders.
702 Impact: Low
704 Permission: java.lang.management.ManagementPermission(monitor)
706 VM.class_hierarchy [options] [arguments]
708 Prints a list of all loaded classes, indented to show the class
709 hierarchy. The name of each class is followed by the ClassLoad‐
710 erData* of its ClassLoader, or "null" if it is loaded by the
711 bootstrap class loader.
712 Impact: Medium --- depends on the number of loaded classes.
714 Permission: java.lang.management.ManagementPermission(monitor)
716 Note:
718 The following options must be specified using either key or
720 key=value syntax.
721 options:
723 • -i: (Optional) Inherited interfaces should be printed. (BOOL‐
725 EAN, false)
726 • -s: (Optional) If a classname is specified, print its sub‐
728 classes in addition to its superclasses. Without this option
729 only the superclasses will be printed. (BOOLEAN, false)
730 arguments:
732 • classname: (Optional) The name of the class whose hierarchy
734 should be printed. If not specified, all class hierarchies
735 are printed. (STRING, no default value)
736 VM.command_line
738 Prints the command line used to start this VM instance.
739 Impact: Low
741 Permission: java.lang.management.ManagementPermission(monitor)
743 VM.dynlibs
745 Prints the loaded dynamic libraries.
746 Impact: Low
748 Permission: java.lang.management.ManagementPermission(monitor)
750 VM.events [options]
752 Print VM event logs
753 Impact: Low --- Depends on event log size.
755 Permission: java.lang.management.ManagementPermission(monitor)
757 options:
759 Note:
761 The following options must be specified using either key or
763 key=value syntax.
764 • log: (Optional) Name of log to be printed. If omitted, all
766 logs are printed. (STRING, no default value)
767 • max: (Optional) Maximum number of events to be printed (newest
769 first). If omitted, all events are printed. (STRING, no de‐
770 fault value)
771 VM.info
773 Prints information about the JVM environment and status.
774 Impact: Low
776 Permission: java.lang.management.ManagementPermission(monitor)
778 VM.log [options]
780 Lists current log configuration, enables/disables/configures a
781 log output, or rotates all logs.
782 Impact: Low
784 Permission: java.lang.management.ManagementPermission(control)
786 options:
788 Note:
790 The following options must be specified using either key or
792 key=value syntax.
793 • output: (Optional) The name or index (#) of output to config‐
795 ure. (STRING, no default value)
796 • output_options: (Optional) Options for the output. (STRING,
798 no default value)
799 • what: (Optional) Configures what tags to log. (STRING, no de‐
801 fault value )
802 • decorators: (Optional) Configures which decorators to use.
804 Use 'none' or an empty value to remove all. (STRING, no de‐
805 fault value)
806 • disable: (Optional) Turns off all logging and clears the log
808 configuration. (BOOLEAN, no default value)
809 • list: (Optional) Lists current log configuration. (BOOLEAN,
811 no default value)
812 • rotate: (Optional) Rotates all logs. (BOOLEAN, no default
814 value)
815 VM.flags [options]
817 Prints the VM flag options and their current values.
818 Impact: Low
820 Permission: java.lang.management.ManagementPermission(monitor)
822 Note:
824 The following options must be specified using either key or
826 key=value syntax.
827 options:
829 • -all: (Optional) Prints all flags supported by the VM (BOOL‐
831 EAN, false).
832 VM.metaspace [options]
834 Prints the statistics for the metaspace
835 Impact: Medium --- Depends on number of classes loaded.
837 Permission: java.lang.management.ManagementPermission(monitor)
839 Note:
841 The following options must be specified using either key or
843 key=value syntax.
844 options:
846 • basic: (Optional) Prints a basic summary (does not need a
848 safepoint). (BOOLEAN, false)
849 • show-loaders: (Optional) Shows usage by class loader. (BOOL‐
851 EAN, false)
852 • show-classes: (Optional) If show-loaders is set, shows loaded
854 classes for each loader. (BOOLEAN, false)
855 • by-chunktype: (Optional) Break down numbers by chunk type.
857 (BOOLEAN, false)
858 • by-spacetype: (Optional) Break down numbers by loader type.
860 (BOOLEAN, false)
861 • vslist: (Optional) Shows details about the underlying virtual
863 space. (BOOLEAN, false)
864 • scale: (Optional) Memory usage in which to scale. Valid val‐
866 ues are: 1, KB, MB or GB (fixed scale) or "dynamic" for a dy‐
867 namically chosen scale. (STRING, dynamic)
868 VM.native_memory [options]
870 Prints native memory usage
871 Impact: Medium
873 Permission: java.lang.management.ManagementPermission(monitor)
875 Note:
877 The following options must be specified using either key or
879 key=value syntax.
880 options:
882 • summary: (Optional) Requests runtime to report current memory
884 summary, which includes total reserved and committed memory,
885 along with memory usage summary by each subsystem. (BOOLEAN,
886 false)
887 • detail: (Optional) Requests runtime to report memory alloca‐
889 tion >= 1K by each callsite. (BOOLEAN, false)
890 • baseline: (Optional) Requests runtime to baseline current mem‐
892 ory usage, so it can be compared against in later time.
893 (BOOLEAN, false)
894 • summary.diff: (Optional) Requests runtime to report memory
896 summary comparison against previous baseline. (BOOLEAN,
897 false)
898 • detail.diff: (Optional) Requests runtime to report memory de‐
900 tail comparison against previous baseline, which shows the
901 memory allocation activities at different callsites. (BOOL‐
902 EAN, false)
903 • statistics: (Optional) Prints tracker statistics for tuning
905 purpose. (BOOLEAN, false)
906 • scale: (Optional) Memory usage in which scale, KB, MB or GB
908 (STRING, KB)
909 VM.print_touched_methods
911 Prints all methods that have ever been touched during the life‐
912 time of this JVM.
913 Impact: Medium --- depends on Java content.
915 VM.set_flag [arguments]
917 Sets the VM flag option by using the provided value.
918 Impact: Low
920 Permission: java.lang.management.ManagementPermission(control)
922 arguments:
924 • flag name: The name of the flag that you want to set (STRING,
926 no default value)
927 • string value: (Optional) The value that you want to set
929 (STRING, no default value)
930 VM.stringtable [options]
932 Dumps the string table.
933 Impact: Medium --- depends on the Java content.
935 Permission: java.lang.management.ManagementPermission(monitor)
937 Note:
939 The following options must be specified using either key or
941 key=value syntax.
942 options:
944 • -verbose: (Optional) Dumps the content of each string in the
946 table (BOOLEAN, false)
947 VM.symboltable [options]
949 Dumps the symbol table.
950 Impact: Medium --- depends on the Java content.
952 Permission: java.lang.management.ManagementPermission(monitor)
954 Note:
956 The following options must be specified using either key or
958 key=value syntax).
959 options:
961 • -verbose: (Optional) Dumps the content of each symbol in the
963 table (BOOLEAN, false)
964 VM.systemdictionary
966 Prints the statistics for dictionary hashtable sizes and bucket
967 length.
968 Impact: Medium
970 Permission: java.lang.management.ManagementPermission(monitor)
972 Note:
974 The following options must be specified using either key or
976 key=value syntax.
977 options:
979 • verbose: (Optional) Dump the content of each dictionary entry
981 for all class loaders (BOOLEAN, false) .
982 VM.system_properties
984 Prints the system properties.
985 Impact: Low
987 Permission: java.util.PropertyPermission(*, read)
989 VM.uptime [options]
991 Prints the VM uptime.
992 Impact: Low
994 Note:
996 The following options must be specified using either key or
998 key=value syntax.
999 options:
1001 • -date: (Optional) Adds a prefix with the current date (BOOL‐
1003 EAN, false)
1004 VM.version
1006 Prints JVM version information.
1007 Impact: Low
1009 Permission: java.util.PropertyPermission(java.vm.version, read)
1011JDK 19 2022 JCMD(1)