'\" t

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.\"

.\" Title: jstat

.\" Language: English

.\" Date: 03 March 2015

.\" SectDesc: Monitoring Tools

.\" Software: JDK 8

.\" Arch: generic

.\" Part Number: E38207-04

.\" Doc ID: JSSON

.\"

.if n .pl 99999

.TH "jstat" "1" "03 March 2015" "JDK 8" "Monitoring Tools"

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.\" -----------------------------------------------------------------

.SH "NAME"

jstat \- Monitors Java Virtual Machine (JVM) statistics\&. This command is experimental and unsupported\&.

.SH "SYNOPSIS"

.sp

.if n \{\

.RS 4

.\}

.nf

\fBjstat\fR [ \fIgeneralOption\fR | \fIoutputOptions vmid\fR [ \fIinterval\fR[s|ms] [ \fIcount \fR] ]

.fi

.if n \{\

.RE

.\}

.PP

\fIgeneralOption\fR

.RS 4

A single general command\-line option

\fB\-help\fR

or

\fB\-options\fR\&. See General Options\&.

.RE

.PP

\fIoutputOptions\fR

.RS 4

One or more output options that consist of a single

\fBstatOption\fR, plus any of the

\fB\-t\fR,

\fB\-h\fR, and

\fB\-J\fR

options\&. See Output Options\&.

.RE

.PP

\fIvmid\fR

.RS 4

Virtual machine identifier, which is a string that indicates the target JVM\&. The general syntax is the following:

.sp

.if n \{\

.RS 4

.\}

.nf

\fB[protocol:][//]lvmid[@hostname[:port]/servername]\fR

.fi

.if n \{\

.RE

.\}

The syntax of the

\fBvmid\fR

string corresponds to the syntax of a URI\&. The

\fBvmid\fR

string can vary from a simple integer that represents a local JVM to a more complex construction that specifies a communications protocol, port number, and other implementation\-specific values\&. See Virtual Machine Identifier\&.

.RE

.PP

\fIinterval\fR [s|ms]

.RS 4

Sampling interval in the specified units, seconds (s) or milliseconds (ms)\&. Default units are milliseconds\&. Must be a positive integer\&. When specified, the

\fBjstat\fR

command produces its output at each interval\&.

.RE

.PP

\fIcount\fR

.RS 4

Number of samples to display\&. The default value is infinity which causes the

\fBjstat\fR

command to display statistics until the target JVM terminates or the

\fBjstat\fR

command is terminated\&. This value must be a positive integer\&.

.RE

.SH "DESCRIPTION"

.PP

The

\fBjstat\fR

command displays performance statistics for an instrumented Java HotSpot VM\&. The target JVM is identified by its virtual machine identifier, or

\fBvmid\fR

option\&.

.SH "VIRTUAL MACHINE IDENTIFIER"

.PP

The syntax of the

\fBvmid\fR

string corresponds to the syntax of a URI:

.sp

.if n \{\

.RS 4

.\}

.nf

\fB[protocol:][//]lvmid[@hostname[:port]/servername]\fR

.fi

.if n \{\

.RE

.\}

.PP

\fIprotocol\fR

.RS 4

The communications protocol\&. If the

\fIprotocol\fR

value is omitted and a host name is not specified, then the default protocol is a platform\-specific optimized local protocol\&. If the

\fIprotocol\fR

value is omitted and a host name is specified, then the default protocol is

\fBrmi\fR\&.

.RE

.PP

\fIlvmid\fR

.RS 4

The local virtual machine identifier for the target JVM\&. The

\fBlvmid\fR

is a platform\-specific value that uniquely identifies a JVM on a system\&. The

\fBlvmid\fR

is the only required component of a virtual machine identifier\&. The

\fBlvmid\fR

is typically, but not necessarily, the operating system\*(Aqs process identifier for the target JVM process\&. You can use the

\fBjps\fR

command to determine the

\fBlvmid\fR\&. Also, you can determine the

\fBlvmid\fR

on Solaris, Linux, and OS X platforms with the

\fBps\fR

command, and on Windows with the Windows Task Manager\&.

.RE

.PP

\fIhostname\fR

.RS 4

A hostname or IP address that indicates the target host\&. If the

\fIhostname\fR

value is omitted, then the target host is the local host\&.

.RE

.PP

\fIport\fR

.RS 4

The default port for communicating with the remote server\&. If the

\fIhostname\fR

value is omitted or the

\fIprotocol\fR

value specifies an optimized, local protocol, then the

\fIport\fR

value is ignored\&. Otherwise, treatment of the

\fBport\fR

parameter is implementation\-specific\&. For the default

\fBrmi\fR

protocol, the port value indicates the port number for the rmiregistry on the remote host\&. If the

\fIport\fR

value is omitted and the

\fIprotocol\fR

value indicates

\fBrmi\fR, then the default rmiregistry port (1099) is used\&.

.RE

.PP

\fIservername\fR

.RS 4

The treatment of the

\fBservername\fR

parameter depends on implementation\&. For the optimized local protocol, this field is ignored\&. For the

\fBrmi\fR

protocol, it represents the name of the RMI remote object on the remote host\&.

.RE

.SH "OPTIONS"

.PP

The

\fBjstat\fR

command supports two types of options, general options and output options\&. General options cause the

\fBjstat\fR

command to display simple usage and version information\&. Output options determine the content and format of the statistical output\&.

.PP

All options and their functionality are subject to change or removal in future releases\&.

.SS "General Options"

.PP

If you specify one of the general options, then you cannot specify any other option or parameter\&.

.PP

\-help

.RS 4

Displays a help message\&.

.RE

.PP

\-options

.RS 4

Displays a list of static options\&. See Output Options\&.

.RE

.SS "Output Options"

.PP

If you do not specify a general option, then you can specify output options\&. Output options determine the content and format of the

\fBjstat\fR

command\*(Aqs output, and consist of a single

\fBstatOption\fR, plus any of the other output options (\fB\-h\fR,

\fB\-t\fR, and

\fB\-J\fR)\&. The

\fBstatOption\fR

must come first\&.

.PP

Output is formatted as a table, with columns that are separated by spaces\&. A header row with titles describes the columns\&. Use the

\fB\-h\fR

option to set the frequency at which the header is displayed\&. Column header names are consistent among the different options\&. In general, if two options provide a column with the same name, then the data source for the two columns is the same\&.

.PP

Use the

\fB\-t\fR

option to display a time stamp column, labeled Timestamp as the first column of output\&. The Timestamp column contains the elapsed time, in seconds, since the target JVM started\&. The resolution of the time stamp is dependent on various factors and is subject to variation due to delayed thread scheduling on heavily loaded systems\&.

.PP

Use the interval and count parameters to determine how frequently and how many times, respectively, the

\fBjstat\fR

command displays its output\&.

.PP

\fBNote:\fR

Do not to write scripts to parse the

\fBjstat\fR

command\*(Aqs output because the format might change in future releases\&. If you write scripts that parse

\fBjstat\fR

command output, then expect to modify them for future releases of this tool\&.

.PP

\-\fIstatOption\fR

.RS 4

Determines the statistics information the

\fBjstat\fR

command displays\&. The following lists the available options\&. Use the

\fB\-options\fR

general option to display the list of options for a particular platform installation\&. See Stat Options and Output\&.

.sp

\fBclass\fR: Displays statistics about the behavior of the class loader\&.

.sp

\fBcompiler\fR: Displays statistics about the behavior of the Java HotSpot VM Just\-in\-Time compiler\&.

.sp

\fBgc\fR: Displays statistics about the behavior of the garbage collected heap\&.

.sp

\fBgccapacity\fR: Displays statistics about the capacities of the generations and their corresponding spaces\&.

.sp

\fBgccause\fR: Displays a summary about garbage collection statistics (same as

\fB\-gcutil\fR), with the cause of the last and current (when applicable) garbage collection events\&.

.sp

\fBgcnew\fR: Displays statistics of the behavior of the new generation\&.

.sp

\fBgcnewcapacity\fR: Displays statistics about the sizes of the new generations and its corresponding spaces\&.

.sp

\fBgcold\fR: Displays statistics about the behavior of the old generation and metaspace statistics\&.

.sp

\fBgcoldcapacity\fR: Displays statistics about the sizes of the old generation\&.

.sp

\fBgcmetacapacity\fR: Displays statistics about the sizes of the metaspace\&.

.sp

\fBgcutil\fR: Displays a summary about garbage collection statistics\&.

.sp

\fBprintcompilation\fR: Displays Java HotSpot VM compilation method statistics\&.

.RE

.PP

\-h \fIn\fR

.RS 4

Displays a column header every

\fIn\fR

samples (output rows), where

\fIn\fR

is a positive integer\&. Default value is 0, which displays the column header the first row of data\&.

.RE

.PP

\-t

.RS 4

Displays a timestamp column as the first column of output\&. The time stamp is the time since the start time of the target JVM\&.

.RE

.PP

\-J\fIjavaOption\fR

.RS 4

Passes

\fBjavaOption\fR

to the Java application launcher\&. For example,

\fB\-J\-Xms48m\fR

sets the startup memory to 48 MB\&. For a complete list of options, see

java(1)\&.

.RE

.SS "Stat Options and Output"

.PP

The following information summarizes the columns that the

\fBjstat\fR

command outputs for each

\fIstatOption\fR\&.

.PP

\-class \fIoption\fR

.RS 4

Class loader statistics\&.

.sp

\fBLoaded\fR: Number of classes loaded\&.

.sp

\fBBytes\fR: Number of kBs loaded\&.

.sp

\fBUnloaded\fR: Number of classes unloaded\&.

.sp

\fBBytes\fR: Number of Kbytes unloaded\&.

.sp

\fBTime\fR: Time spent performing class loading and unloading operations\&.

.RE

.PP

\-compiler \fIoption\fR

.RS 4

Java HotSpot VM Just\-in\-Time compiler statistics\&.

.sp

\fBCompiled\fR: Number of compilation tasks performed\&.

.sp

\fBFailed\fR: Number of compilations tasks failed\&.

.sp

\fBInvalid\fR: Number of compilation tasks that were invalidated\&.

.sp

\fBTime\fR: Time spent performing compilation tasks\&.

.sp

\fBFailedType\fR: Compile type of the last failed compilation\&.

.sp

\fBFailedMethod\fR: Class name and method of the last failed compilation\&.

.RE

.PP

\-gc \fIoption\fR

.RS 4

Garbage\-collected heap statistics\&.

.sp

\fBS0C\fR: Current survivor space 0 capacity (kB)\&.

.sp

\fBS1C\fR: Current survivor space 1 capacity (kB)\&.

.sp

\fBS0U\fR: Survivor space 0 utilization (kB)\&.

.sp

\fBS1U\fR: Survivor space 1 utilization (kB)\&.

.sp

\fBEC\fR: Current eden space capacity (kB)\&.

.sp

\fBEU\fR: Eden space utilization (kB)\&.

.sp

\fBOC\fR: Current old space capacity (kB)\&.

.sp

\fBOU\fR: Old space utilization (kB)\&.

.sp

\fBMC\fR: Metaspace capacity (kB)\&.

.sp

\fBMU\fR: Metacspace utilization (kB)\&.

.sp

\fBCCSC\fR: Compressed class space capacity (kB)\&.

.sp

\fBCCSU\fR: Compressed class space used (kB)\&.

.sp

\fBYGC\fR: Number of young generation garbage collection events\&.

.sp

\fBYGCT\fR: Young generation garbage collection time\&.

.sp

\fBFGC\fR: Number of full GC events\&.

.sp

\fBFGCT\fR: Full garbage collection time\&.

.sp

\fBGCT\fR: Total garbage collection time\&.

.RE

.PP

\-gccapacity \fIoption\fR

.RS 4

Memory pool generation and space capacities\&.

.sp

\fBNGCMN\fR: Minimum new generation capacity (kB)\&.

.sp

\fBNGCMX\fR: Maximum new generation capacity (kB)\&.

.sp

\fBNGC\fR: Current new generation capacity (kB)\&.

.sp

\fBS0C\fR: Current survivor space 0 capacity (kB)\&.

.sp

\fBS1C\fR: Current survivor space 1 capacity (kB)\&.

.sp

\fBEC\fR: Current eden space capacity (kB)\&.

.sp

\fBOGCMN\fR: Minimum old generation capacity (kB)\&.

.sp

\fBOGCMX\fR: Maximum old generation capacity (kB)\&.

.sp

\fBOGC\fR: Current old generation capacity (kB)\&.

.sp

\fBOC\fR: Current old space capacity (kB)\&.

.sp

\fBMCMN\fR: Minimum metaspace capacity (kB)\&.

.sp

\fBMCMX\fR: Maximum metaspace capacity (kB)\&.

.sp

\fBMC\fR: Metaspace capacity (kB)\&.

.sp

\fBCCSMN\fR: Compressed class space minimum capacity (kB)\&.

.sp

\fBCCSMX\fR: Compressed class space maximum capacity (kB)\&.

.sp

\fBCCSC\fR: Compressed class space capacity (kB)\&.

.sp

\fBYGC\fR: Number of young generation GC events\&.

.sp

\fBFGC\fR: Number of full GC events\&.

.RE

.PP

\-gccause \fIoption\fR

.RS 4

This option displays the same summary of garbage collection statistics as the

\fB\-gcutil\fR

option, but includes the causes of the last garbage collection event and (when applicable) the current garbage collection event\&. In addition to the columns listed for

\fB\-gcutil\fR, this option adds the following columns\&.

.sp

\fBLGCC\fR: Cause of last garbage collection

.sp

\fBGCC\fR: Cause of current garbage collection

.RE

.PP

\-gcnew \fIoption\fR

.RS 4

New generation statistics\&.

.sp

\fBS0C\fR: Current survivor space 0 capacity (kB)\&.

.sp

\fBS1C\fR: Current survivor space 1 capacity (kB)\&.

.sp

\fBS0U\fR: Survivor space 0 utilization (kB)\&.

.sp

\fBS1U\fR: Survivor space 1 utilization (kB)\&.

.sp

\fBTT\fR: Tenuring threshold\&.

.sp

\fBMTT\fR: Maximum tenuring threshold\&.

.sp

\fBDSS\fR: Desired survivor size (kB)\&.

.sp

\fBEC\fR: Current eden space capacity (kB)\&.

.sp

\fBEU\fR: Eden space utilization (kB)\&.

.sp

\fBYGC\fR: Number of young generation GC events\&.

.sp

\fBYGCT\fR: Young generation garbage collection time\&.

.RE

.PP

\-gcnewcapacity \fIoption\fR

.RS 4

New generation space size statistics\&.

.sp

\fBNGCMN\fR: Minimum new generation capacity (kB)\&.

.sp

\fBNGCMX\fR: Maximum new generation capacity (kB)\&.

.sp

\fBNGC\fR: Current new generation capacity (kB)\&.

.sp

\fBS0CMX\fR: Maximum survivor space 0 capacity (kB)\&.

.sp

\fBS0C\fR: Current survivor space 0 capacity (kB)\&.

.sp

\fBS1CMX\fR: Maximum survivor space 1 capacity (kB)\&.

.sp

\fBS1C\fR: Current survivor space 1 capacity (kB)\&.

.sp