jcmd(1) JDK Commands jcmd(1)
NAME
jcmd - send diagnostic command requests to a running Java Virtual Ma-
chine (JVM)
SYNOPSIS
jcmd [pid | main-class] command... | PerfCounter.print | -f filename
jcmd [-l]
jcmd -h
pid When used, the jcmd utility sends the diagnostic command request
to the process ID for the Java process.
main-class
When used, the jcmd utility sends the diagnostic command request
to all Java processes with the specified name of the main class.
command
The command must be a valid jcmd command for the selected JVM.
The list of available commands for jcmd is obtained by running
the help command (jcmd pid help) where pid is the process ID for
the running Java process. If the pid is 0, commands will be
sent to all Java processes. The main class argument will be
used to match, either partially or fully, the class used to
start Java. If no options are given, it lists the running Java
process identifiers with the main class and command-line argu-
ments that were used to launch the process (the same as using
-l).
Perfcounter.print
Prints the performance counters exposed by the specified Java
process.
-f filename
Reads and executes commands from a specified file, filename.
-l Displays the list of Java Virtual Machine process identifiers
that are not running in a separate docker process along with the
main class and command-line arguments that were used to launch
the process. If the JVM is in a docker process, you must use
tools such as ps to look up the PID.
Note:
Using jcmd without arguments is the same as using jcmd -l.
-h Displays the jcmd utility's command-line help.
DESCRIPTION
The jcmd utility is used to send diagnostic command requests to the
JVM. It must be used on the same machine on which the JVM is running,
and have the same effective user and group identifiers that were used
to launch the JVM. Each diagnostic command has its own set of argu-
ments. To display the description, syntax, and a list of available ar-
guments for a diagnostic command, use the name of the command as the
argument. For example:
jcmd pid help command
If arguments contain spaces, then you must surround them with single or
double quotation marks (' or "). In addition, you must escape single
or double quotation marks with a backslash (\) to prevent the operating
system shell from processing quotation marks. Alternatively, you can
surround these arguments with single quotation marks and then with dou-
ble quotation marks (or with double quotation marks and then with sin-
gle quotation marks).
If you specify the process identifier (pid) or the main class
(main-class) as the first argument, then the jcmd utility sends the di-
agnostic command request to the Java process with the specified identi-
fier or to all Java processes with the specified name of the main
class. You can also send the diagnostic command request to all avail-
able Java processes by specifying 0 as the process identifier.
COMMANDS FOR JCMD
The command must be a valid jcmd diagnostic command for the selected
JVM. The list of available commands for jcmd is obtained by running
the help command (jcmd pid help) where pid is the process ID for a run-
ning Java process. If the pid is 0, commands will be sent to all Java
processes. The main class argument will be used to match, either par-
tially or fully, the class used to start Java. If no options are giv-
en, it lists the running Java process identifiers that are not in sepa-
rate docker processes along with the main class and command-line argu-
ments that were used to launch the process (the same as using -l).
The following commands are available:
help [options] [arguments]
For more information about a specific command.
arguments:
o command name: The name of the command for which we want help
(STRING, no default value)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o -all: (Optional) Show help for all commands (BOOLEAN, false) .
Compiler.codecache
Prints code cache layout and bounds.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
Compiler.codelist
Prints all compiled methods in code cache that are alive.
Impact: Medium
Permission: java.lang.management.ManagementPermission(monitor)
Compiler.queue
Prints methods queued for compilation.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
Compiler.directives_add *filename* *arguments*
Adds compiler directives from a file.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
arguments:
filename: The name of the directives file (STRING, no default
value)
Compiler.directives_clear
Remove all compiler directives.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
Compiler.directives_print
Prints all active compiler directives.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
Compiler.directives_remove
Remove latest added compiler directive.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
GC.class_histogram [options]
Provides statistics about the Java heap usage.
Impact: High --- depends on Java heap size and content.
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The options must be specified using either key or key=value syn-
tax.
options:
o -all: (Optional) Inspects all objects, including unreachable
objects (BOOLEAN, false)
GC.finalizer_info
Provides information about the Java finalization queue.
Impact: Medium
Permission: java.lang.management.ManagementPermission(monitor)
GC.heap_dump [options] [arguments]
Generates a HPROF format dump of the Java heap.
Impact: High --- depends on the Java heap size and content. Re-
quest a full GC unless the -all option is specified.
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o -all: (Optional) Dump all objects, including unreachable ob-
jects (BOOLEAN, false)
arguments:
o filename: The name of the dump file (STRING, no default value)
GC.heap_info
Provides generic Java heap information.
Impact: Medium
Permission: java.lang.management.ManagementPermission(monitor)
GC.run Calls java.lang.System.gc().
Impact: Medium --- depends on the Java heap size and content.
GC.run_finalization
Calls java.lang.System.runFinalization().
Impact: Medium --- depends on the Java content.
JFR.check [options]
Show information about a running flight recording
Impact: Low
Note:
The options must be specified using either key or key=value syn-
tax. If no parameters are entered, information for all active
recordings is shown.
options:
o name: (Optional) Name of the flight recording. (STRING, no
default value)
o verbose: (Optional) Flag for printing the event settings for
the recording (BOOLEAN, false)
JFR.configure [options]
Set the parameters for a flight recording
Impact: Low
Note:
The options must be specified using either key or key=value syn-
tax. If no parameters are entered, the current settings are
displayed.
options:
o globalbuffercount: (Optional) Number of global buffers. This
option is a legacy option: change the memorysize parameter to
alter the number of global buffers. This value cannot be
changed once JFR has been initalized. (STRING, default deter-
mined by the value for memorysize)
o globalbuffersize: (Optional) Size of the global buffers, in
bytes. This option is a legacy option: change the memorysize
parameter to alter the size of the global buffers. This value
cannot be changed once JFR has been initalized. (STRING, de-
fault determined by the value for memorysize)
o maxchunksize: (Optional) Maximum size of an individual data
chunk in bytes if one of the following suffixes is not used:
'm' or 'M' for megabytes OR 'g' or 'G' for gigabytes. This
value cannot be changed once JFR has been initialized.
(STRING, 12M)
o memorysize: (Optional) Overall memory size, in bytes if one of
the following suffixes is not used: 'm' or 'M' for megabytes
OR 'g' or 'G' for gigabytes. This value cannot be changed
once JFR has been initialized. (STRING, 10M)
o repositorypath: (Optional) Path to the location where record-
ings are stored until they are written to a permanent file.
(STRING, The default location is the temporary directory for
the operating system. On Linux operating systems, the tempo-
rary directory is /tmp. On Windwows, the temporary directory
is specified by the TMP environment variable.)
o stackdepth: (Optional) Stack depth for stack traces. Setting
this value greater than the default of 64 may cause a perfor-
mance degradation. This value cannot be changed once JFR has
been initialized. (LONG, 64)
o thread_buffer_size: (Optional) Local buffer size for each
thread in bytes if one of the following suffixes is not used:
'k' or 'K' for kilobytes or 'm' or 'M' for megabytes. Over-
riding this parameter could reduce performance and is not rec-
ommended. This value cannot be changed once JFR has been ini-
tialized. (STRING, 8k)
o samplethreads: (Optional) Flag for activating thread sampling.
(BOOLEAN, true)
JFR.dump [options]
Write data to a file while a flight recording is running
Impact: Low
Note:
The options must be specified using either key or key=value syn-
tax. No options are required. The recording continues to run
after the data is written.
options:
o begin: (Optional) Specify the time from which recording data
will be included in the dump file. The format is specified as
local time. (STRING, no default value)
o end: (Optional) Specify the time to which recording data will
be included in the dump file. The format is specified as lo-
cal time. (STRING, no default value)
Note: For both begin and end, the time must be in a format
that can be read by java.time.LocalTime::parse(STRING), ja-
va.time.LocalDateTime::parse(STRING) or java.time.In-
stant::parse(STRING). For example, "13:20:15",
"2020-03-17T09:00:00" or "2020-03-17T09:00:00Z".
Note: begin and end times correspond to the timestamps found
within the recorded information in the flight recording data.
Another option is to use a time relative to the current time
that is specified by a negative integer followed by "s", "m"
or "h". For example, "-12h", "-15m" or "-30s"
o filename: (Optional) Name of the file to which the flight
recording data is dumped. If no filename is given, a filename
is generated from the PID and the current date. The filename
may also be a directory in which case, the filename is gener-
ated from the PID and the current date in the specified direc-
tory. (STRING, no default value)
o maxage: (Optional) Length of time for dumping the flight
recording data to a file. (INTEGER followed by 's' for sec-
onds 'm' for minutes or 'h' for hours, no default value)
o maxsize: (Optional) Maximum size for the amount of data to
dump from a flight recording in bytes if one of the following
suffixes is not used: 'm' or 'M' for megabytes OR 'g' or 'G'
for gigabytes. (STRING, no default value)
o name: (Optional) Name of the recording. If no name is given,
data from all recordings is dumped. (STRING, no default val-
ue)
o path-to-gc-root: (Optional) Flag for saving the path to
garbage collection (GC) roots at the time the recording data
is dumped. The path information is useful for finding memory
leaks but collecting it can cause the application to pause for
a short period of time. Turn on this flag only when you have
an application that you suspect has a memory leak. (BOOLEAN,
false)
JFR.start [options]
Start a flight recording
Impact: Low
Note:
The options must be specified using either key or key=value syn-
tax. If no parameters are entered, then a recording is started
with default values.
options:
o delay: (Optional) Length of time to wait before starting to
record (INTEGER followed by 's' for seconds 'm' for minutes or
'h' for hours, 0s)
o disk: (Optional) Flag for also writing the data to disk while
recording (BOOLEAN, true)
o dumponexit: (Optional) Flag for writing the recording to disk
when the Java Virtual Machine (JVM) shuts down. If set to
'true' and no value is given for filename, the recording is
written to a file in the directory where the process was
started. The file name is a system-generated name that con-
tains the process ID, the recording ID and the current time
stamp. (For example: id-1-2019_12_12_10_41.jfr) (BOOLEAN,
false)
o duration: (Optional) Length of time to record. Note that 0s
means forever (INTEGER followed by 's' for seconds 'm' for
minutes or 'h' for hours, 0s)
o filename: (Optional) Name of the file to which the flight
recording data is written when the recording is stopped. If
no filename is given, a filename is generated from the PID and
the current date and is placed in the directory where the
process was started. The filename may also be a directory in
which case, the filename is generated from the PID and the
current date in the specified directory. (STRING, no default
value)
o maxage: (Optional) Maximum time to keep the recorded data on
disk. This parameter is valid only when the disk parameter is
set to true. Note 0s means forever. (INTEGER followed by 's'
for seconds 'm' for minutes or 'h' for hours, 0s)
o maxsize: (Optional) Maximum size of the data to keep on disk
in bytes if one of the following suffixes is not used: 'm' or
'M' for megabytes OR 'g' or 'G' for gigabytes. This parameter
is valid only when the disk parameter is set to 'true'. The
value must not be less than the value for the maxchunksize pa-
rameter set with the JFR.configure command. (STRING, 0 (no
maximum size))
o name: (Optional) Name of the recording. If no name is provid-
ed, a name is generated. Make note of the generated name that
is shown in the response to the command so that you can use it
with other commands. (STRING, system-generated default name)
o path-to-gc-root: (Optional) Flag for saving the path to
garbage collection (GC) roots at the end of a recording. The
path information is useful for finding memory leaks but col-
lecting it is time consuming. Turn on this flag only when you
have an application that you suspect has a memory leak. If
the settings parameter is set to 'profile', then the informa-
tion collected includes the stack trace from where the poten-
tial leaking object was allocated. (BOOLEAN, false)
o settings: (Optional) Name of the settings file that identifies
which events to record. To specify more than one file, sepa-
rate the names with a comma (','). Include the path if the
file is not in JAVA-HOME/lib/jfr. The following profiles are
included with the JDK in the JAVA-HOME/lib/jfr directory: 'de-
fault.jfc': collects a predefined set of information with low
overhead, so it has minimal impact on performance and can be
used with recordings that run continuously; 'profile.jfc':
Provides more data than the 'default.jfc' profile, but with
more overhead and impact on performance. Use this configura-
tion for short periods of time when more information is need-
ed. Use none to start a recording without a predefined con-
figuration file. (STRING, JAVA-HOME/lib/jfr/default.jfc)
JFR.stop [options]
Stop a flight recording
Impact: Low
Note:
The options must be specified using either key or key=value syn-
tax. If no parameters are entered, then no recording is
stopped.
options:
o filename: (Optional) Name of the file to which the recording
is written when the recording is stopped. If no path is pro-
vided, the data from the recording is discarded. (STRING, no
default value)
o name: (Optional) Name of the recording (STRING, no default
value)
JVMTI.agent_load [arguments]
Loads JVMTI native agent.
Impact: Low
Permission: java.lang.management.ManagementPermission(control)
arguments:
o library path: Absolute path of the JVMTI agent to load.
(STRING, no default value)
o agent option: (Optional) Option string to pass the agent.
(STRING, no default value)
JVMTI.data_dump
Signals the JVM to do a data-dump request for JVMTI.
Impact: High
Permission: java.lang.management.ManagementPermission(monitor)
ManagementAgent.start [options]
Starts remote management agent.
Impact: Low --- no impact
Note:
The following options must be specified using either key or
key=value syntax.
options:
o config.file: (Optional) Sets com.sun.management.config.file
(STRING, no default value)
o jmxremote.host: (Optional) Sets com.sun.management.jmxre-
mote.host (STRING, no default value)
o jmxremote.port: (Optional) Sets com.sun.management.jmxre-
mote.port (STRING, no default value)
o jmxremote.rmi.port: (Optional) Sets com.sun.management.jmxre-
mote.rmi.port (STRING, no default value)
o jmxremote.ssl: (Optional) Sets com.sun.management.jmxre-
mote.ssl (STRING, no default value)
o jmxremote.registry.ssl: (Optional) Sets com.sun.manage-
ment.jmxremote.registry.ssl (STRING, no default value)
o jmxremote.authenticate: (Optional) Sets com.sun.manage-
ment.jmxremote.authenticate (STRING, no default value)
o jmxremote.password.file: (Optional) Sets com.sun.manage-
ment.jmxremote.password.file (STRING, no default value)
o jmxremote.access.file: (Optional) Sets com.sun.manage-
ment.jmxremote.acce ss.file (STRING, no default value)
o jmxremote.login.config: (Optional) Sets com.sun.manage-
ment.jmxremote.log in.config (STRING, no default value)
o jmxremote.ssl.enabled.cipher.suites: (Optional) Sets
com.sun.management.
o jmxremote.ssl.enabled.cipher.suite: (STRING, no default value)
o jmxremote.ssl.enabled.protocols: (Optional) Sets com.sun.man-
agement.jmxr emote.ssl.enabled.protocols (STRING, no default
value)
o jmxremote.ssl.need.client.auth: (Optional) Sets com.sun.man-
agement.jmxre mote.need.client.auth (STRING, no default value)
o jmxremote.ssl.config.file: (Optional) Sets com.sun.manage-
ment.jmxremote. ssl_config_file (STRING, no default value)
o jmxremote.autodiscovery: (Optional) Sets com.sun.manage-
ment.jmxremote.au todiscovery (STRING, no default value)
o jdp.port: (Optional) Sets com.sun.management.jdp.port (INT, no
default value)
o jdp.address: (Optional) Sets com.sun.management.jdp.address
(STRING, no default value)
o jdp.source_addr: (Optional) Sets com.sun.manage-
ment.jdp.source_addr (STRING, no default value)
o jdp.ttl: (Optional) Sets com.sun.management.jdp.ttl (INT, no
default value)
o jdp.pause: (Optional) Sets com.sun.management.jdp.pause (INT,
no default value)
o jdp.name: (Optional) Sets com.sun.management.jdp.name (STRING,
no default value)
ManagementAgent.start_local
Starts the local management agent.
Impact: Low --- no impact
ManagementAgent.status
Print the management agent status.
Impact: Low --- no impact
Permission: java.lang.management.ManagementPermission(monitor)
ManagementAgent.stop
Stops the remote management agent.
Impact: Low --- no impact
Thread.print [options]
Prints all threads with stacktraces.
Impact: Medium --- depends on the number of threads.
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o -l: (Optional) Prints java.util.concurrent locks (BOOLEAN,
false)
VM.classloader_stats
Prints statistics about all ClassLoaders.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
VM.class_hierarchy [options] [arguments]
Prints a list of all loaded classes, indented to show the class
hierarchy. The name of each class is followed by the ClassLoad-
erData* of its ClassLoader, or "null" if it is loaded by the
bootstrap class loader.
Impact: Medium --- depends on the number of loaded classes.
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o -i: (Optional) Inherited interfaces should be printed.
(BOOLEAN, false)
o -s: (Optional) If a class name is specified, it prints the
subclasses. If the class name is not specified, only the su-
perclasses are printed. (BOOLEAN, false)
arguments:
o classname: (Optional) The name of the class whose hierarchy
should be printed. If not specified, all class hierarchies
are printed. (STRING, no default value)
VM.command_line
Prints the command line used to start this VM instance.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
VM.dynlibs
Prints the loaded dynamic libraries.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
VM.info
Prints information about the JVM environment and status.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
VM.log [options]
Lists current log configuration, enables/disables/configures a
log output, or rotates all logs.
Impact: Low
Permission: java.lang.management.ManagementPermission(control)
options:
Note:
The following options must be specified using either key or
key=value syntax.
o output: (Optional) The name or index (#) of output to config-
ure. (STRING, no default value)
o output_options: (Optional) Options for the output. (STRING,
no default value)
o what: (Optional) Configures what tags to log. (STRING, no de-
fault value )
o decorators: (Optional) Configures which decorators to use.
Use 'none' or an empty value to remove all. (STRING, no de-
fault value)
o disable: (Optional) Turns off all logging and clears the log
configuration. (BOOLEAN, no default value)
o list: (Optional) Lists current log configuration. (BOOLEAN,
no default value)
o rotate: (Optional) Rotates all logs. (BOOLEAN, no default
value)
VM.flags [options]
Prints the VM flag options and their current values.
Impact: Low
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o -all: (Optional) Prints all flags supported by the VM
(BOOLEAN, false).
VM.native_memory [options]
Prints native memory usage
Impact: Medium
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o summary: (Optional) Requests runtime to report current memory
summary, which includes total reserved and committed memory,
along with memory usage summary by each subsystem. (BOOLEAN,
false)
o detail: (Optional) Requests runtime to report memory alloca-
tion >= 1K by each callsite. (BOOLEAN, false)
o baseline: (Optional) Requests runtime to baseline current mem-
ory usage, so it can be compared against in later time.
(BOOLEAN, false)
o summary.diff: (Optional) Requests runtime to report memory
summary comparison against previous baseline. (BOOLEAN,
false)
o detail.diff: (Optional) Requests runtime to report memory de-
tail comparison against previous baseline, which shows the
memory allocation activities at different callsites.
(BOOLEAN, false)
o shutdown: (Optional) Requests runtime to shutdown itself and
free the memory used by runtime. (BOOLEAN, false)
o statistics: (Optional) Prints tracker statistics for tuning
purpose. (BOOLEAN, false)
o scale: (Optional) Memory usage in which scale, KB, MB or GB
(STRING, KB)
VM.print_touched_methods
Prints all methods that have ever been touched during the life-
time of this JVM.
Impact: Medium --- depends on Java content.
VM.set_flag [arguments]
Sets the VM flag option by using the provided value.
Impact: Low
Permission: java.lang.management.ManagementPermission(control)
arguments:
o flag name: The name of the flag that you want to set (STRING,
no default value)
o string value: (Optional) The value that you want to set
(STRING, no default value)
VM.stringtable [options]
Dumps the string table.
Impact: Medium --- depends on the Java content.
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o -verbose: (Optional) Dumps the content of each string in the
table (BOOLEAN, false)
VM.symboltable [options]
Dumps the symbol table.
Impact: Medium --- depends on the Java content.
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax).
options:
o -verbose: (Optional) Dumps the content of each symbol in the
table (BOOLEAN, false)
VM.systemdictionary
Prints the statistics for dictionary hashtable sizes and bucket
length.
Impact: Medium
Permission: java.lang.management.ManagementPermission(monitor)
Note:
The following options must be specified using either key or
key=value syntax.
options:
o verbose: (Optional) Dump the content of each dictionary entry
for all class loaders (BOOLEAN, false) .
VM.system_properties
Prints the system properties.
Impact: Low
Permission: java.util.PropertyPermission(*, read)
VM.uptime [options]
Prints the VM uptime.
Impact: Low
Note:
The following options must be specified using either key or
key=value syntax.
options:
o -date: (Optional) Adds a prefix with the current date
(BOOLEAN, false)
VM.version
Prints JVM version information.
Impact: Low
Permission: java.util.PropertyPermission(java.vm.version, read)
JDK 15 2020 jcmd(1)
openjdk 15.0.2 - Generated Tue Feb 23 16:15:02 CST 2021