blob: 405df2649808d785689294f6948249d6b84a5ee6 [file] [log] [blame]
rgallardb6435452013-11-25 20:19:02 -08001'\" t
2.\" Copyright (c) 2004, 2013, Oracle and/or its affiliates. All rights reserved.
3.\"
4.\" DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5.\"
6.\" This code is free software; you can redistribute it and/or modify it
7.\" under the terms of the GNU General Public License version 2 only, as
8.\" published by the Free Software Foundation.
9.\"
10.\" This code is distributed in the hope that it will be useful, but WITHOUT
11.\" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12.\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13.\" version 2 for more details (a copy is included in the LICENSE file that
14.\" accompanied this code).
15.\"
16.\" You should have received a copy of the GNU General Public License version
17.\" 2 along with this work; if not, write to the Free Software Foundation,
18.\" Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19.\"
20.\" Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21.\" or visit www.oracle.com if you need additional information or have any
22.\" questions.
23.\"
24.\" Arch: generic
25.\" Software: JDK 8
26.\" Date: 10 May 2011
27.\" SectDesc: Monitoring Tools
28.\" Title: jstat.1
29.\"
30.if n .pl 99999
31.TH jstat 1 "10 May 2011" "JDK 8" "Monitoring Tools"
32.\" -----------------------------------------------------------------
33.\" * Define some portability stuff
34.\" -----------------------------------------------------------------
35.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
36.\" http://bugs.debian.org/507673
37.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
38.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
39.ie \n(.g .ds Aq \(aq
40.el .ds Aq '
41.\" -----------------------------------------------------------------
42.\" * set default formatting
43.\" -----------------------------------------------------------------
44.\" disable hyphenation
45.nh
46.\" disable justification (adjust text to left margin only)
47.ad l
48.\" -----------------------------------------------------------------
49.\" * MAIN CONTENT STARTS HERE *
50.\" -----------------------------------------------------------------
tbell16c34dd2009-05-04 18:28:26 -070051
rgallardb6435452013-11-25 20:19:02 -080052.SH NAME
53jstat \- Monitors Java Virtual Machine (JVM) statistics\&. This command is experimental and unsupported\&.
54.SH SYNOPSIS
55.sp
56.nf
tbell16c34dd2009-05-04 18:28:26 -070057
rgallardb6435452013-11-25 20:19:02 -080058\fBjstat\fR [ \fIgeneralOption\fR | \fIoutputOptions vmid\fR [ \fIinterval\fR[s|ms] [ \fIcount \fR] ]
59.fi
60.sp
61.TP
62\fIgeneralOption\fR
63A single general command-line option \f3-help\fR or \f3-options\fR\&. See General Options\&.
64.TP
65\fIoutputOptions\fR
66One or more output options that consist of a single \f3statOption\fR, plus any of the \f3-t\fR, \f3-h\fR, and \f3-J\fR options\&. See Output Options\&.
67.TP
68\fIvmid\fR
69Virtual machine identifier, which is a string that indicates the target JVM\&. The general syntax is the following:
70.sp
71.nf
72\f3[protocol:][//]lvmid[@hostname[:port]/servername]\fP
73.fi
74.nf
75\f3\fP
76.fi
77.sp
tbell16c34dd2009-05-04 18:28:26 -070078
tbell16c34dd2009-05-04 18:28:26 -070079
rgallardb6435452013-11-25 20:19:02 -080080The syntax of the \f3vmid\fR string corresponds to the syntax of a URI\&. The \f3vmid\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\&.
81.TP
82\fIinterval\fR [s|ms]
83Sampling interval in the specified units, seconds (s) or milliseconds (ms)\&. Default units are milliseconds\&. Must be a positive integer\&. When specified, the \f3jstat\fR command produces its output at each interval\&.
84.TP
85\fIcount\fR
86Number of samples to display\&. The default value is infinity which causes the \f3jstat\fR command to display statistics until the target JVM terminates or the \f3jstat\fR command is terminated\&. This value must be a positive integer\&.
87.SH DESCRIPTION
88The \f3jstat\fR command displays performance statistics for an instrumented Java HotSpot VM\&. The target JVM is identified by its virtual machine identifier, or \f3vmid\fR option\&.
89.SH VIRTUAL\ MACHINE\ IDENTIFIER
90The syntax of the \f3vmid\fR string corresponds to the syntax of a URI:
91.sp
92.nf
93\f3[protocol:][//]lvmid[@hostname[:port]/servername]\fP
94.fi
95.nf
96\f3\fP
97.fi
98.sp
99.TP
100\fIprotocol\fR
101The 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 \f3rmi\fR\&.
102.TP
103\fIlvmid\fR
104The local virtual machine identifier for the target JVM\&. The \f3lvmid\fR is a platform-specific value that uniquely identifies a JVM on a system\&. The \f3lvmid\fR is the only required component of a virtual machine identifier\&. The \f3lvmid\fR is typically, but not necessarily, the operating system\&'s process identifier for the target JVM process\&. You can use the \f3jps\fR command to determine the \f3lvmid\fR\&. Also, you can determine the \f3lvmid\fR on UNIX platforms with the \f3ps\fR command, and on Windows with the Windows Task Manager\&.
105.TP
106\fIhostname\fR
107A hostname or IP address that indicates the target host\&. If the \fIhostname\fR value is omitted, then the target host is the local host\&.
108.TP
109\fIport\fR
110The 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 \f3port\fR parameter is implementation-specific\&. For the default \f3rmi\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 \f3rmi\fR, then the default rmiregistry port (1099) is used\&.
111.TP
112\fIservername\fR
113The treatment of the \f3servername\fR parameter depends on implementation\&. For the optimized local protocol, this field is ignored\&. For the \f3rmi\fR protocol, it represents the name of the RMI remote object on the remote host\&.
114.SH OPTIONS
115The \f3jstat\fR command supports two types of options, general options and output options\&. General options cause the \f3jstat\fR command to display simple usage and version information\&. Output options determine the content and format of the statistical output\&.
116.PP
117All options and their functionality are subject to change or removal in future releases\&.
118.SS GENERAL\ OPTIONS
119If you specify one of the general options, then you cannot specify any other option or parameter\&.
120.TP
121-help
122.br
123Displays a help message\&.
124.TP
125-options
126.br
127Displays a list of static options\&. See Output Options\&.
128.SS OUTPUT\ OPTIONS
129If you do not specify a general option, then you can specify output options\&. Output options determine the content and format of the \f3jstat\fR command\&'s output, and consist of a single \f3statOption\fR, plus any of the other output options (\f3-h\fR, \f3-t\fR, and \f3-J\fR)\&. The \f3statOption\fR must come first\&.
130.PP
131Output is formatted as a table, with columns that are separated by spaces\&. A header row with titles describes the columns\&. Use the \f3-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\&.
132.PP
133Use the \f3-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\&.
134.PP
135Use the interval and count parameters to determine how frequently and how many times, respectively, the \f3jstat\fR command displays its output\&.
136.PP
137\fINote:\fR Do not to write scripts to parse the \f3jstat\fR command\&'s output because the format might change in future releases\&. If you write scripts that parse \f3jstat\fR command output, then expect to modify them for future releases of this tool\&.
138.TP
139-\fIstatOption\fR
140.br
141Determines the statistics information the \f3jstat\fR command displays\&. The following lists the available options\&. Use the \f3-options\fR general option to display the list of options for a particular platform installation\&. See Stat Options and Output\&.
tbell16c34dd2009-05-04 18:28:26 -0700142
rgallardb6435452013-11-25 20:19:02 -0800143\f3class\fR: Displays statistics about the behavior of the class loader\&.
tbell16c34dd2009-05-04 18:28:26 -0700144
rgallardb6435452013-11-25 20:19:02 -0800145\f3compiler\fR: Displays statistics about the behavior of the Java HotSpot VM Just-in-Time compiler\&.
tbell16c34dd2009-05-04 18:28:26 -0700146
rgallardb6435452013-11-25 20:19:02 -0800147\f3gc\fR: Displays statistics about the behavior of the garbage collected heap\&.
tbell16c34dd2009-05-04 18:28:26 -0700148
rgallardb6435452013-11-25 20:19:02 -0800149\f3gccapacity\fR: Displays statistics about the capacities of the generations and their corresponding spaces\&.
tbell16c34dd2009-05-04 18:28:26 -0700150
rgallardb6435452013-11-25 20:19:02 -0800151\f3gccause\fR: Displays a summary about garbage collection statistics (same as \f3-gcutil\fR), with the cause of the last and current (when applicable) garbage collection events\&.
tbell16c34dd2009-05-04 18:28:26 -0700152
rgallardb6435452013-11-25 20:19:02 -0800153\f3gcnew\fR: Displays statistics of the behavior of the new generation\&.
tbell16c34dd2009-05-04 18:28:26 -0700154
rgallardb6435452013-11-25 20:19:02 -0800155\f3gcnewcapacity\fR: Displays statistics about the sizes of the new generations and its corresponding spaces\&.
tbell16c34dd2009-05-04 18:28:26 -0700156
rgallardb6435452013-11-25 20:19:02 -0800157\f3gcold\fR: Displays statistics about the behavior of the old generation and Metaspace Statistics\&.
tbell16c34dd2009-05-04 18:28:26 -0700158
rgallardb6435452013-11-25 20:19:02 -0800159\f3gcoldcapacity\fR: Displays statistics about the sizes of the old generation\&.
tbell16c34dd2009-05-04 18:28:26 -0700160
rgallardb6435452013-11-25 20:19:02 -0800161\f3gcmetacapacity\fR: Displays statistics about the sizes of the metaspace\&.
tbell16c34dd2009-05-04 18:28:26 -0700162
rgallardb6435452013-11-25 20:19:02 -0800163\f3gcutil\fR: Displays a summary about garbage collection statistics\&.
tbell16c34dd2009-05-04 18:28:26 -0700164
rgallardb6435452013-11-25 20:19:02 -0800165\f3printcompilation\fR: Displays Java HotSpot VM compilation method statistics\&.
166.TP
167-h \fIn\fR
duke6e45e102007-12-01 00:00:00 +0000168.br
rgallardb6435452013-11-25 20:19:02 -0800169Displays 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\&.
170.TP
171-t
duke6e45e102007-12-01 00:00:00 +0000172.br
rgallardb6435452013-11-25 20:19:02 -0800173Display sa timestamp column as the first column of output\&. The time stamp is the time since the start time of the target JVM\&.
174.TP
175-J\fIjavaOption\fR
duke6e45e102007-12-01 00:00:00 +0000176.br
rgallardb6435452013-11-25 20:19:02 -0800177Passes \f3javaOption\fR to the Java application launcher\&. For example, \f3-J-Xms48m\fR sets the startup memory to 48 MB\&. For a complete list of options, see java(1)\&.
178.SS STAT\ OPTIONS\ AND\ OUTPUT
179The following information summarizes the columns that the \f3jstat\fR command outputs for each \fIstatOption\fR\&.
180.TP
181-class \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000182.br
rgallardb6435452013-11-25 20:19:02 -0800183Class loader statistics\&.
tbell16c34dd2009-05-04 18:28:26 -0700184
rgallardb6435452013-11-25 20:19:02 -0800185\f3Loaded\fR: Number of classes loaded\&.
tbell16c34dd2009-05-04 18:28:26 -0700186
rgallardb6435452013-11-25 20:19:02 -0800187\f3Bytes\fR: Number of KBs loaded\&.
tbell16c34dd2009-05-04 18:28:26 -0700188
rgallardb6435452013-11-25 20:19:02 -0800189\f3Unloaded\fR: Number of classes unloaded\&.
tbell16c34dd2009-05-04 18:28:26 -0700190
rgallardb6435452013-11-25 20:19:02 -0800191\f3Bytes\fR: Number of Kbytes unloaded\&.
tbell16c34dd2009-05-04 18:28:26 -0700192
rgallardb6435452013-11-25 20:19:02 -0800193\f3Time\fR: Time spent performing class loading and unloading operations\&.
194.TP
195-compiler \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000196.br
rgallardb6435452013-11-25 20:19:02 -0800197Java HotSpot VM Just-in-Time compiler statistics\&.
198
199\f3Compiled\fR: Number of compilation tasks performed\&.
200
201\f3Failed\fR: Number of compilations tasks failed\&.
202
203\f3Invalid\fR: Number of compilation tasks that were invalidated\&.
204
205\f3Time\fR: Time spent performing compilation tasks\&.
206
207\f3FailedType\fR: Compile type of the last failed compilation\&.
208
209\f3FailedMethod\fR: Class name and method of the last failed compilation\&.
210.TP
211-gc \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000212.br
rgallardb6435452013-11-25 20:19:02 -0800213Garbage-collected heap statistics\&.
214
215\f3S0C\fR: Current survivor space 0 capacity (KB)\&.
216
217\f3S1C\fR: Current survivor space 1 capacity (KB)\&.
218
219\f3S0U\fR: Survivor space 0 utilization (KB)\&.
220
221\f3S1U\fR: Survivor space 1 utilization (KB)\&.
222
223\f3EC\fR: Current eden space capacity (KB)\&.
224
225\f3EU\fR: Eden space utilization (KB)\&.
226
227\f3OC\fR: Current old space capacity (KB)\&.
228
229\f3OU\fR: Old space utilization (KB)\&.
230
231\f3MC\fR: Metaspace capacity (KB)\&.
232
233\f3MU\fR: Metacspace utilization (KB)\&.
234
235\f3YGC\fR: Number of young generation garbage collection events\&.
236
237\f3YGCT\fR: Young generation garbage collection time\&.
238
239\f3FGC\fR: Number of full GC events\&.
240
241\f3FGCT\fR: Full garbage collection time\&.
242
243\f3GCT\fR: Total garbage collection time\&.
244.TP
245-gccapacity \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000246.br
rgallardb6435452013-11-25 20:19:02 -0800247Memory pool generation and space capacities\&.
248
249\f3NGCMN\fR: Minimum new generation capacity (KB)\&.
250
251\f3NGCMX\fR: Maximum new generation capacity (KB)\&.
252
253\f3NGC\fR: Current new generation capacity (KB)\&.
254
255\f3S0C\fR: Current survivor space 0 capacity (KB)\&.
256
257\f3S1C\fR: Current survivor space 1 capacity (KB)\&.
258
259\f3EC\fR: Current eden space capacity (KB)\&.
260
261\f3OGCMN\fR: Minimum old generation capacity (KB)\&.
262
263\f3OGCMX\fR: Maximum old generation capacity (KB)\&.
264
265\f3OGC\fR: Current old generation capacity (KB)\&.
266
267\f3OC\fR: Current old space capacity (KB)\&.
268
269\f3MCMN\fR: Minimum metaspace capacity (KB)\&.
270
271\f3MCMX\fR: Maximum metaspace capacity (KB)\&.
272
273\f3MC\fR: Metaspace capacity (KB)\&.
274
275\f3YGC\fR: Number of Young generation GC Events\&.
276
277\f3FGC\fR: Number of Full GC Events\&.
278.TP
279-gccause \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000280.br
rgallardb6435452013-11-25 20:19:02 -0800281This option displays the same summary of garbage collection statistics as the \f3-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 \f3-gcutil\fR, this option adds the following columns\&.
282
283Garbage collection statistics, including garbage collection Events\&.
284
285\f3LGCC\fR: Cause of last garbage collection\&.
286
287\f3GCC\fR: Cause of current garbage collection\&.
288.TP
289-gcnew \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000290.br
rgallardb6435452013-11-25 20:19:02 -0800291New generation statistics\&.
292
293\f3S0C\fR: Current survivor space 0 capacity (KB)\&.
294
295\f3S1C\fR: Current survivor space 1 capacity (KB)\&.
296
297\f3S0U\fR: Survivor space 0 utilization (KB)\&.
298
299\f3S1U\fR: Survivor space 1 utilization (KB)\&.
300
301\f3TT\fR: Tenuring threshold\&.
302
303\f3MTT\fR: Maximum tenuring threshold\&.
304
305\f3DSS\fR: Desired survivor size (KB)\&.
306
307\f3EC\fR: Current eden space capacity (KB)\&.
308
309\f3EU\fR: Eden space utilization (KB)\&.
310
311\f3YGC\fR: Number of young generation GC events\&.
312
313\f3YGCT\fR: Young generation garbage collection time\&.
314.TP
315-gcnewcapacity \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000316.br
rgallardb6435452013-11-25 20:19:02 -0800317New generation space size statistics\&.
tbell16c34dd2009-05-04 18:28:26 -0700318
rgallardb6435452013-11-25 20:19:02 -0800319NGCMN: Minimum new generation capacity (KB)\&.
320
321\f3NGCMX\fR: Maximum new generation capacity (KB)\&.
322
323\f3NGC\fR: Current new generation capacity (KB)\&.
324
325\f3S0CMX\fR: Maximum survivor space 0 capacity (KB)\&.
326
327\f3S0C\fR: Current survivor space 0 capacity (KB)\&.
328
329\f3S1CMX\fR: Maximum survivor space 1 capacity (KB)\&.
330
331\f3S1C\fR: Current survivor space 1 capacity (KB)\&.
332
333\f3ECMX\fR: Maximum eden space capacity (KB)\&.
334
335\f3EC\fR: Current eden space capacity (KB)\&.
336
337\f3YGC\fR: Number of young generation GC events\&.
338
339\f3FGC\fR: Number of Full GC Events\&.
340.TP
341-gcold \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000342.br
rgallardb6435452013-11-25 20:19:02 -0800343old and permanent generation statistics\&.
duke6e45e102007-12-01 00:00:00 +0000344
rgallardb6435452013-11-25 20:19:02 -0800345\f3MC\fR: Metaspace capacity (KB)\&.
346
347\f3MU\fR: Metaspace utilization (KB)\&.
348
349\f3OC\fR: Current old space capacity (KB)\&.
350
351\f3OU\fR: old space utilization (KB)\&.
352
353\f3YGC\fR: Number of young generation GC events\&.
354
355\f3FGC\fR: Number of full GC events\&.
356
357\f3FGCT\fR: Full garbage collection time\&.
358
359\f3GCT\fR: Total garbage collection time\&.
360.TP
361-gcoldcapacity \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000362.br
rgallardb6435452013-11-25 20:19:02 -0800363Old generation statistics\&.
duke6e45e102007-12-01 00:00:00 +0000364
rgallardb6435452013-11-25 20:19:02 -0800365\f3OGCMN\fR: Minimum old generation capacity (KB)\&.
366
367\f3OGCMX\fR: Maximum old generation capacity (KB)\&.
368
369\f3OGC\fR: Current old generation capacity (KB)\&.
370
371\f3OC\fR: Current old space capacity (KB)\&.
372
373\f3YGC\fR: Number of young generation GC events\&.
374
375\f3FGC\fR: Number of full GC events\&.
376
377\f3FGCT\fR: Full garbage collection time\&.
378
379\f3GCT\fR: Total garbage collection time\&.
380.TP
381-gcmetacapacity \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000382.br
rgallardb6435452013-11-25 20:19:02 -0800383Permanent generation statistics\&.
duke6e45e102007-12-01 00:00:00 +0000384
rgallardb6435452013-11-25 20:19:02 -0800385\f3MCMN\fR: Minimum metaspace capacity (KB)\&.
386
387\f3MCMX\fR: Maximum metaspace capacity (KB)\&.
388
389\f3MC\fR: Metaspace capacity (KB)\&.
390
391\f3YGC\fR: Number of young generation GC events\&.
392
393\f3FGC\fR: Number of full GC events\&.
394
395\f3FGCT\fR: Full garbage collection time\&.
396
397\f3GCT\fR: Total garbage collection time\&.
398.TP
399-gcutil \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000400.br
rgallardb6435452013-11-25 20:19:02 -0800401Summary of garbage collection statistics\&.
duke6e45e102007-12-01 00:00:00 +0000402
rgallardb6435452013-11-25 20:19:02 -0800403\f3S0\fR: Survivor space 0 utilization as a percentage of the space\&'s current capacity\&.
404
405\f3S1\fR: Survivor space 1 utilization as a percentage of the space\&'s current capacity\&.
406
407\f3E\fR: Eden space utilization as a percentage of the space\&'s current capacity\&.
408
409\f3O\fR: Old space utilization as a percentage of the space\&'s current capacity\&.
410
411\f3M\fR: Metaspace utilization as a percentage of the space\&'s current capacity\&.
412
413\f3YGC\fR: Number of young generation GC events\&.
414
415\f3YGCT\fR: Young generation garbage collection time\&.
416
417\f3FGC\fR: Number of full GC events\&.
418
419\f3FGCT\fR: Full garbage collection time\&.
420
421\f3GCT\fR: Total garbage collection time\&.
422.TP
423-printcompilation \fIoption\fR
duke6e45e102007-12-01 00:00:00 +0000424.br
rgallardb6435452013-11-25 20:19:02 -0800425Java HotSpot VM compiler method statistics\&.
duke6e45e102007-12-01 00:00:00 +0000426
rgallardb6435452013-11-25 20:19:02 -0800427\f3Compiled\fR: Number of compilation tasks performed by the most recently compiled method\&.
duke6e45e102007-12-01 00:00:00 +0000428
rgallardb6435452013-11-25 20:19:02 -0800429\f3Size\fR: Number of bytes of byte code of the most recently compiled method\&.
duke6e45e102007-12-01 00:00:00 +0000430
rgallardb6435452013-11-25 20:19:02 -0800431\f3Type\fR: Compilation type of the most recently compiled method\&.
duke6e45e102007-12-01 00:00:00 +0000432
rgallardb6435452013-11-25 20:19:02 -0800433\f3Method\fR: Class name and method name identifying the most recently compiled method\&. Class name uses slash (/) instead of dot (\&.) as a name space separator\&. Method name is the method within the specified class\&. The format for these two fields is consistent with the HotSpot \f3-XX:+PrintComplation\fR option\&.
434.SH EXAMPLES
435This section presents some examples of monitoring a local JVM with an \fIlvmid\fR of 21891\&.
436.SS THE\ GCUTIL\ OPTION
437This example attaches to lvmid 21891 and takes 7 samples at 250 millisecond intervals and displays the output as specified by the -\f3gcutil\fR option\&.
438.PP
439The output of this example shows that a young generation collection occurred between the third and fourth sample\&. The collection took 0\&.001 seconds and promoted objects from the eden space (E) to the old space (O), resulting in an increase of old space utilization from 9\&.49% to 9\&.51%\&. Before the collection, the survivor space was 12\&.44% utilized, but after this collection it is only 7\&.74% utilized\&.
440.sp
441.nf
442\f3jstat \-gcutil 21891 250 7\fP
443.fi
444.nf
445\f3 S0 S1 E O M YGC YGCT FGC FGCT GCT\fP
446.fi
447.nf
448\f30\&.00 99\&.74 13\&.49 7\&.86 95\&.82 3 0\&.124 0 0\&.000 0\&.124\fP
449.fi
450.nf
451\f30\&.00 99\&.74 13\&.49 7\&.86 95\&.82 3 0\&.124 0 0\&.000 0\&.124\fP
452.fi
453.nf
454\f30\&.00 99\&.74 13\&.49 7\&.86 95\&.82 3 0\&.124 0 0\&.000 0\&.124\fP
455.fi
456.nf
457\f30\&.00 99\&.74 13\&.49 7\&.86 95\&.82 3 0\&.124 0 0\&.000 0\&.124\fP
458.fi
459.nf
460\f30\&.00 99\&.74 13\&.80 7\&.86 95\&.82 3 0\&.124 0 0\&.000 0\&.124\fP
461.fi
462.nf
463\f30\&.00 99\&.74 13\&.80 7\&.86 95\&.82 3 0\&.124 0 0\&.000 0\&.124\fP
464.fi
465.nf
466\f30\&.00 99\&.74 13\&.80 7\&.86 95\&.82 3 0\&.124 0 0\&.000 0\&.124\fP
467.fi
468.nf
469\f3\fP
470.fi
471.sp
472.SS REPEAT\ THE\ COLUMN\ HEADER\ STRING
473This example attaches to lvmid 21891 and takes samples at 250 millisecond intervals and displays the output as specified by \f3-gcutil\fR option\&. In addition, it uses the \f3-h3\fR option to output the column header after every 3 lines of data\&.
474.PP
475In addition to showing the repeating header string, this example shows that between the second and third samples, a young GC occurred\&. Its duration was 0\&.001 seconds\&. The collection found enough active data that the survivor space 0 utilization (S0U) would have exceeded the desired survivor Size (DSS)\&. As a result, objects were promoted to the old generation (not visible in this output), and the tenuring threshold (TT) was lowered from 31 to 2\&.
476.PP
477Another collection occurs between the fifth and sixth samples\&. This collection found very few survivors and returned the tenuring threshold to 31\&.
478.sp
479.nf
480\f3jstat \-gcnew \-h3 21891 250\fP
481.fi
482.nf
483\f3 S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT\fP
484.fi
485.nf
486\f3 64\&.0 64\&.0 0\&.0 31\&.7 31 31 32\&.0 512\&.0 178\&.6 249 0\&.203\fP
487.fi
488.nf
489\f3 64\&.0 64\&.0 0\&.0 31\&.7 31 31 32\&.0 512\&.0 355\&.5 249 0\&.203\fP
490.fi
491.nf
492\f3 64\&.0 64\&.0 35\&.4 0\&.0 2 31 32\&.0 512\&.0 21\&.9 250 0\&.204\fP
493.fi
494.nf
495\f3 S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT\fP
496.fi
497.nf
498\f3 64\&.0 64\&.0 35\&.4 0\&.0 2 31 32\&.0 512\&.0 245\&.9 250 0\&.204\fP
499.fi
500.nf
501\f3 64\&.0 64\&.0 35\&.4 0\&.0 2 31 32\&.0 512\&.0 421\&.1 250 0\&.204\fP
502.fi
503.nf
504\f3 64\&.0 64\&.0 0\&.0 19\&.0 31 31 32\&.0 512\&.0 84\&.4 251 0\&.204\fP
505.fi
506.nf
507\f3 S0C S1C S0U S1U TT MTT DSS EC EU YGC YGCT\fP
508.fi
509.nf
510\f3 64\&.0 64\&.0 0\&.0 19\&.0 31 31 32\&.0 512\&.0 306\&.7 251 0\&.204\fP
511.fi
512.nf
513\f3\fP
514.fi
515.sp
516.SS INCLUDE\ A\ TIME\ STAMP\ FOR\ EACH\ SAMPLE
517This example attaches to lvmid 21891 and takes 3 samples at 250 millisecond intervals\&. The \f3-t\fR option is used to generate a time stamp for each sample in the first column\&.
518.PP
519The Timestamp column reports the elapsed time in seconds since the start of the target JVM\&. In addition, the \f3-gcoldcapacity\fR output shows the old generation capacity (OGC) and the old space capacity (OC) increasing as the heap expands to meet allocation or promotion demands\&. The old generation capacity (OGC) has grown to from 11,696 KB to 13820 KB after the eighty-first full garbage collection (FGC)\&. The maximum capacity of the generation (and space) is 60,544 KB (OGCMX), so it still has room to expand\&.
520.sp
521.nf
522\f3Timestamp OGCMN OGCMX OGC OC YGC FGC FGCT GCT\fP
523.fi
524.nf
525\f3 150\&.1 1408\&.0 60544\&.0 11696\&.0 11696\&.0 194 80 2\&.874 3\&.799\fP
526.fi
527.nf
528\f3 150\&.4 1408\&.0 60544\&.0 13820\&.0 13820\&.0 194 81 2\&.938 3\&.863\fP
529.fi
530.nf
531\f3 150\&.7 1408\&.0 60544\&.0 13820\&.0 13820\&.0 194 81 2\&.938 3\&.863\fP
532.fi
533.nf
534\f3\fP
535.fi
536.sp
537.SS MONITOR\ INSTRUMENTATION\ FOR\ A\ REMOTE\ JVM
538This example attaches to lvmid 40496 on the system named remote\&.domain using the \f3-gcutil\fR option, with samples taken every second indefinitely\&.
539.PP
540The lvmid is combined with the name of the remote host to construct a \fIvmid\fR of \f340496@remote\&.domain\fR\&. This vmid results in the use of the \f3rmi\fR protocol to communicate to the default \f3jstatd\fR server on the remote host\&. The \f3jstatd\fR server is located using the rmiregistry on \f3remote\&.domain\fR that is bound to the default rmiregistry port (port 1099)\&.
541.sp
542.nf
543\f3jstat \-gcutil 40496@remote\&.domain 1000\fP
544.fi
545.nf
546\f3\fI\&.\&.\&. output omitted\fR\fP
547.fi
548.nf
549\f3\fP
550.fi
551.sp
552.SH SEE\ ALSO
553.TP 0.2i
554\(bu
555java(1)
556.TP 0.2i
557\(bu
558jps(1)
559.TP 0.2i
560\(bu
561jstatd(1)
562.TP 0.2i
563\(bu
564rmiregistry(1)
565.RE
566.br
567'pl 8.5i
568'bp