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  24 .TH "JSTAT" "1" "2018" "JDK 13" "JDK Commands"
  25 .hy
  26 .SH NAME
  27 .PP
  28 jstat \- monitor JVM statistics
  29 .SH SYNOPSIS
  30 .PP
  31 \f[B]Note:\f[R] This command is experimental\ and unsupported.
  32 .PP
  33 \f[CB]jstat\f[R] \f[I]generalOptions\f[R]
  34 .PP
  35 \f[CB]jstat\f[R] \f[I]outputOptions\f[R] [\f[CB]\-t\f[R]] [\f[CB]\-h\f[R]
  36 \f[I]lines\f[R]] \f[I]vmid\f[R] [\f[I]interval\f[R] [\f[I]count\f[R]]]
  37 .TP
  38 .B \f[I]generalOptions\f[R]
  39 A single general command\-line option.
  40 See \f[B]General Options\f[R].
  41 .RS
  42 .RE
  43 .TP
  44 .B \f[I]outputOptions\f[R]
  45 An option reported by the \f[CB]\-options\f[R] option.
  46 One or more output options that consist of a single \f[CB]statOption\f[R],
  47 plus any of the \f[CB]\-t\f[R], \f[CB]\-h\f[R], and \f[CB]\-J\f[R] options.
  48 See \f[B]Output Options for the jstat Command\f[R].
  49 .RS
  50 .RE
  51 .TP
  52 .B \f[CB]\-t\f[R]
  53 Displays a time\-stamp column as the first column of output.
  54 The time stamp is the time since the start time of the target JVM.
  55 .RS
  56 .RE
  57 .TP
  58 .B \f[CB]\-h\f[R] \f[I]n\f[R]
  59 Displays a column header every \f[I]n\f[R] samples (output rows), where
  60 \f[I]n\f[R] is a positive integer.
  61 The default value is \f[CB]0\f[R], which displays the column header of the
  62 first row of data.
  63 .RS
  64 .RE
  65 .TP
  66 .B \f[I]vmid\f[R]
  67 A virtual machine identifier, which is a string that indicates the
  68 target JVM.
  69 See \f[B]Virtual Machine Identifier\f[R].
  70 .RS
  71 .RE
  72 .TP
  73 .B \f[I]interval\f[R]
  74 The sampling interval in the specified units, seconds (s) or
  75 milliseconds (ms).
  76 Default units are milliseconds.
  77 This must be a positive integer.
  78 When specified, the \f[CB]jstat\f[R] command produces its output at each
  79 interval.
  80 .RS
  81 .RE
  82 .TP
  83 .B \f[I]count\f[R]
  84 The number of samples to display.
  85 The default value is infinity, which causes the \f[CB]jstat\f[R] command
  86 to display statistics until the target JVM terminates or the
  87 \f[CB]jstat\f[R] command is terminated.
  88 This value must be a positive integer.
  89 .RS
  90 .RE
  91 .SH DESCRIPTION
  92 .PP
  93 The \f[CB]jstat\f[R] command displays performance statistics for an
  94 instrumented Java HotSpot VM.
  95 The target JVM is identified by its virtual machine identifier, or
  96 \f[CB]vmid\f[R] option.
  97 .PP
  98 The \f[CB]jstat\f[R] command supports two types of options, general
  99 options and output options.
 100 General options cause the \f[CB]jstat\f[R] command to display simple usage
 101 and version information.
 102 Output options determine the content and format of the statistical
 103 output.
 104 .PP
 105 All options and their functionality are subject to change or removal in
 106 future releases.
 107 .SH GENERAL OPTIONS
 108 .PP
 109 If you specify one of the general options, then you can\[aq]t specify
 110 any other option or parameter.
 111 .TP
 112 .B \f[CB]\-help\f[R]
 113 Displays a help message.
 114 .RS
 115 .RE
 116 .TP
 117 .B \f[CB]\-options\f[R]
 118 Displays a list of static options.
 119 See \f[B]Output Options for the jstat Command\f[R].
 120 .RS
 121 .RE
 122 .SH OUTPUT OPTIONS FOR THE JSTAT COMMAND
 123 .PP
 124 If you don\[aq]t specify a general option, then you can specify output
 125 options.
 126 Output options determine the content and format of the \f[CB]jstat\f[R]
 127 command\[aq]s output, and consist of a single \f[CB]statOption\f[R], plus
 128 any of the other output options (\f[CB]\-h\f[R], \f[CB]\-t\f[R], and
 129 \f[CB]\-J\f[R]).
 130 The \f[CB]statOption\f[R] must come first.
 131 .PP
 132 Output is formatted as a table, with columns that are separated by
 133 spaces.
 134 A header row with titles describes the columns.
 135 Use the \f[CB]\-h\f[R] option to set the frequency at which the header is
 136 displayed.
 137 Column header names are consistent among the different options.
 138 In general, if two options provide a column with the same name, then the
 139 data source for the two columns is the same.
 140 .PP
 141 Use the \f[CB]\-t\f[R] option to display a time\-stamp column, labeled
 142 Timestamp as the first column of output.
 143 The Timestamp column contains the elapsed time, in seconds, since the
 144 target JVM started.
 145 The resolution of the time stamp is dependent on various factors and is
 146 subject to variation due to delayed thread scheduling on heavily loaded
 147 systems.
 148 .PP
 149 Use the interval and count parameters to determine how frequently and
 150 how many times, respectively, the \f[CB]jstat\f[R] command displays its
 151 output.
 152 .PP
 153 \f[B]Note:\f[R]
 154 .PP
 155 Don\[aq]t write scripts to parse the \f[CB]jstat\f[R] command\[aq]s output
 156 because the format might change in future releases.
 157 If you write scripts that parse the \f[CB]jstat\f[R] command output, then
 158 expect to modify them for future releases of this tool.
 159 .TP
 160 .B \f[CB]\-statOption\f[R]
 161 Determines the statistics information that the \f[CB]jstat\f[R] command
 162 displays.
 163 The following lists the available options.
 164 Use the \f[CB]\-options\f[R] general option to display the list of options
 165 for a particular platform installation.
 166 See \f[B]Stat Options and Output\f[R].
 167 .RS
 168 .PP
 169 \f[CB]class\f[R]: Displays statistics about the behavior of the class
 170 loader.
 171 .PP
 172 \f[CB]compiler\f[R]: Displays statistics about the behavior of the Java
 173 HotSpot VM Just\-in\-Time compiler.
 174 .PP
 175 \f[CB]gc\f[R]: Displays statistics about the behavior of the garbage
 176 collected heap.
 177 .PP
 178 \f[CB]gccapacity\f[R]: Displays statistics about the capacities of the
 179 generations and their corresponding spaces.
 180 .PP
 181 \f[CB]gccause\f[R]: Displays a summary about garbage collection statistics
 182 (same as \f[CB]\-gcutil\f[R]), with the cause of the last and current
 183 (when applicable) garbage collection events.
 184 .PP
 185 \f[CB]gcnew\f[R]: Displays statistics about the behavior of the new
 186 generation.
 187 .PP
 188 \f[CB]gcnewcapacity\f[R]: Displays statistics about the sizes of the new
 189 generations and their corresponding spaces.
 190 .PP
 191 \f[CB]gcold\f[R]: Displays statistics about the behavior of the old
 192 generation and metaspace statistics.
 193 .PP
 194 \f[CB]gcoldcapacity\f[R]: Displays statistics about the sizes of the old
 195 generation.
 196 .PP
 197 \f[CB]gcmetacapacity\f[R]: Displays statistics about the sizes of the
 198 metaspace.
 199 .PP
 200 \f[CB]gcutil\f[R]: Displays a summary about garbage collection statistics.
 201 .PP
 202 \f[CB]printcompilation\f[R]: Displays Java HotSpot VM compilation method
 203 statistics.
 204 .RE
 205 .TP
 206 .B \f[CB]\-J\f[R]\f[I]javaOption\f[R]
 207 Passes \f[I]javaOption\f[R] to the Java application launcher.
 208 For example, \f[CB]\-J\-Xms48m\f[R] sets the startup memory to 48 MB.
 209 For a complete list of options, see \f[B]java\f[R].
 210 .RS
 211 .RE
 212 .SH STAT OPTIONS AND OUTPUT
 213 .PP
 214 The following information summarizes the columns that the \f[CB]jstat\f[R]
 215 command outputs for each \f[I]statOption\f[R].
 216 .TP
 217 .B \f[CB]\-class\f[R] \f[I]option\f[R]
 218 Class loader statistics.
 219 .RS
 220 .PP
 221 \f[CB]Loaded\f[R]: Number of classes loaded.
 222 .PP
 223 \f[CB]Bytes\f[R]: Number of KB loaded.
 224 .PP
 225 \f[CB]Unloaded\f[R]: Number of classes unloaded.
 226 .PP
 227 \f[CB]Bytes\f[R]: Number of KB loaded.
 228 .PP
 229 \f[CB]Time\f[R]: Time spent performing class loading and unloading
 230 operations.
 231 .RE
 232 .TP
 233 .B \f[CB]\-compiler\f[R] \f[I]option\f[R]
 234 Java HotSpot VM Just\-in\-Time compiler statistics.
 235 .RS
 236 .PP
 237 \f[CB]Compiled\f[R]: Number of compilation tasks performed.
 238 .PP
 239 \f[CB]Failed\f[R]: Number of compilations tasks failed.
 240 .PP
 241 \f[CB]Invalid\f[R]: Number of compilation tasks that were invalidated.
 242 .PP
 243 \f[CB]Time\f[R]: Time spent performing compilation tasks.
 244 .PP
 245 \f[CB]FailedType\f[R]: Compile type of the last failed compilation.
 246 .PP
 247 \f[CB]FailedMethod\f[R]: Class name and method of the last failed
 248 compilation.
 249 .RE
 250 .TP
 251 .B \f[CB]\-gc\f[R] \f[I]option\f[R]
 252 Garbage collected heap statistics.
 253 .RS
 254 .PP
 255 \f[CB]S0C\f[R]: Current survivor space 0 capacity (KB).
 256 .PP
 257 \f[CB]S1C\f[R]: Current survivor space 1 capacity (KB).
 258 .PP
 259 \f[CB]S0U\f[R]: Survivor space 0 utilization (KB).
 260 .PP
 261 \f[CB]S1U\f[R]: Survivor space 1 utilization (KB).
 262 .PP
 263 \f[CB]EC\f[R]: Current eden space capacity (KB).
 264 .PP
 265 \f[CB]EU\f[R]: Eden space utilization (KB).
 266 .PP
 267 \f[CB]OC\f[R]: Current old space capacity (KB).
 268 .PP
 269 \f[CB]OU\f[R]: Old space utilization (KB).
 270 .PP
 271 \f[CB]MC\f[R]: Metaspace Committed Size (KB).
 272 .PP
 273 \f[CB]MU\f[R]: Metaspace utilization (KB).
 274 .PP
 275 \f[CB]CCSC\f[R]: Compressed class committed size (KB).
 276 .PP
 277 \f[CB]CCSU\f[R]: Compressed class space used (KB).
 278 .PP
 279 \f[CB]YGC\f[R]: Number of young generation garbage collection (GC) events.
 280 .PP
 281 \f[CB]YGCT\f[R]: Young generation garbage collection time.
 282 .PP
 283 \f[CB]FGC\f[R]: Number of full GC events.
 284 .PP
 285 \f[CB]FGCT\f[R]: Full garbage collection time.
 286 .PP
 287 \f[CB]GCT\f[R]: Total garbage collection time.
 288 .RE
 289 .TP
 290 .B \f[CB]\-gccapacity\f[R] \f[I]option\f[R]
 291 Memory pool generation and space capacities.
 292 .RS
 293 .PP
 294 \f[CB]NGCMN\f[R]: Minimum new generation capacity (KB).
 295 .PP
 296 \f[CB]NGCMX\f[R]: Maximum new generation capacity (KB).
 297 .PP
 298 \f[CB]NGC\f[R]: Current new generation capacity (KB).
 299 .PP
 300 \f[CB]S0C\f[R]: Current survivor space 0 capacity (KB).
 301 .PP
 302 \f[CB]S1C\f[R]: Current survivor space 1 capacity (KB).
 303 .PP
 304 \f[CB]EC\f[R]: Current eden space capacity (KB).
 305 .PP
 306 \f[CB]OGCMN\f[R]: Minimum old generation capacity (KB).
 307 .PP
 308 \f[CB]OGCMX\f[R]: Maximum old generation capacity (KB).
 309 .PP
 310 \f[CB]OGC\f[R]: Current old generation capacity (KB).
 311 .PP
 312 \f[CB]OC\f[R]: Current old space capacity (KB).
 313 .PP
 314 \f[CB]MCMN\f[R]: Minimum metaspace capacity (KB).
 315 .PP
 316 \f[CB]MCMX\f[R]: Maximum metaspace capacity (KB).
 317 .PP
 318 \f[CB]MC\f[R]: Metaspace Committed Size (KB).
 319 .PP
 320 \f[CB]CCSMN\f[R]: Compressed class space minimum capacity (KB).
 321 .PP
 322 \f[CB]CCSMX\f[R]: Compressed class space maximum capacity (KB).
 323 .PP
 324 \f[CB]CCSC\f[R]: Compressed class committed size (KB).
 325 .PP
 326 \f[CB]YGC\f[R]: Number of young generation GC events.
 327 .PP
 328 \f[CB]FGC\f[R]: Number of full GC events.
 329 .RE
 330 .TP
 331 .B \f[CB]\-gccause\f[R] \f[I]option\f[R]
 332 This option displays the same summary of garbage collection statistics
 333 as the \f[CB]\-gcutil\f[R] option, but includes the causes of the last
 334 garbage collection event and (when applicable), the current garbage
 335 collection event.
 336 In addition to the columns listed for \f[CB]\-gcutil\f[R], this option
 337 adds the following columns:
 338 .RS
 339 .PP
 340 \f[CB]LGCC\f[R]: Cause of last garbage collection
 341 .PP
 342 \f[CB]GCC\f[R]: Cause of current garbage collection
 343 .RE
 344 .TP
 345 .B \f[CB]\-gcnew\f[R] \f[I]option\f[R]
 346 New generation statistics.
 347 .RS
 348 .PP
 349 \f[CB]S0C\f[R]: Current survivor space 0 capacity (KB).
 350 .PP
 351 \f[CB]S1C\f[R]: Current survivor space 1 capacity (KB).
 352 .PP
 353 \f[CB]S0U\f[R]: Survivor space 0 utilization (KB).
 354 .PP
 355 \f[CB]S1U\f[R]: Survivor space 1 utilization (KB).
 356 .PP
 357 \f[CB]TT\f[R]: Tenuring threshold.
 358 .PP
 359 \f[CB]MTT\f[R]: Maximum tenuring threshold.
 360 .PP
 361 \f[CB]DSS\f[R]: Desired survivor size (KB).
 362 .PP
 363 \f[CB]EC\f[R]: Current eden space capacity (KB).
 364 .PP
 365 \f[CB]EU\f[R]: Eden space utilization (KB).
 366 .PP
 367 \f[CB]YGC\f[R]: Number of young generation GC events.
 368 .PP
 369 \f[CB]YGCT\f[R]: Young generation garbage collection time.
 370 .RE
 371 .TP
 372 .B \f[CB]\-gcnewcapacity\f[R] \f[I]option\f[R]
 373 New generation space size statistics.
 374 .RS
 375 .PP
 376 \f[CB]NGCMN\f[R]: Minimum new generation capacity (KB).
 377 .PP
 378 \f[CB]NGCMX\f[R]: Maximum new generation capacity (KB).
 379 .PP
 380 \f[CB]NGC\f[R]: Current new generation capacity (KB).
 381 .PP
 382 \f[CB]S0CMX\f[R]: Maximum survivor space 0 capacity (KB).
 383 .PP
 384 \f[CB]S0C\f[R]: Current survivor space 0 capacity (KB).
 385 .PP
 386 \f[CB]S1CMX\f[R]: Maximum survivor space 1 capacity (KB).
 387 .PP
 388 \f[CB]S1C\f[R]: Current survivor space 1 capacity (KB).
 389 .PP
 390 \f[CB]ECMX\f[R]: Maximum eden space capacity (KB).
 391 .PP
 392 \f[CB]EC\f[R]: Current eden space capacity (KB).
 393 .PP
 394 \f[CB]YGC\f[R]: Number of young generation GC events.
 395 .PP
 396 \f[CB]FGC\f[R]: Number of full GC events.
 397 .RE
 398 .TP
 399 .B \f[CB]\-gcold\f[R] \f[I]option\f[R]
 400 Old generation size statistics.
 401 .RS
 402 .PP
 403 \f[CB]MC\f[R]: Metaspace Committed Size (KB).
 404 .PP
 405 \f[CB]MU\f[R]: Metaspace utilization (KB).
 406 .PP
 407 \f[CB]CCSC\f[R]: Compressed class committed size (KB).
 408 .PP
 409 \f[CB]CCSU\f[R]: Compressed class space used (KB).
 410 .PP
 411 \f[CB]OC\f[R]: Current old space capacity (KB).
 412 .PP
 413 \f[CB]OU\f[R]: Old space utilization (KB).
 414 .PP
 415 \f[CB]YGC\f[R]: Number of young generation GC events.
 416 .PP
 417 \f[CB]FGC\f[R]: Number of full GC events.
 418 .PP
 419 \f[CB]FGCT\f[R]: Full garbage collection time.
 420 .PP
 421 \f[CB]GCT\f[R]: Total garbage collection time.
 422 .RE
 423 .TP
 424 .B \f[CB]\-gcoldcapacity\f[R] \f[I]option\f[R]
 425 Old generation statistics.
 426 .RS
 427 .PP
 428 \f[CB]OGCMN\f[R]: Minimum old generation capacity (KB).
 429 .PP
 430 \f[CB]OGCMX\f[R]: Maximum old generation capacity (KB).
 431 .PP
 432 \f[CB]OGC\f[R]: Current old generation capacity (KB).
 433 .PP
 434 \f[CB]OC\f[R]: Current old space capacity (KB).
 435 .PP
 436 \f[CB]YGC\f[R]: Number of young generation GC events.
 437 .PP
 438 \f[CB]FGC\f[R]: Number of full GC events.
 439 .PP
 440 \f[CB]FGCT\f[R]: Full garbage collection time.
 441 .PP
 442 \f[CB]GCT\f[R]: Total garbage collection time.
 443 .RE
 444 .TP
 445 .B \f[CB]\-gcmetacapacity\f[R] \f[I]option\f[R]
 446 Metaspace size statistics.
 447 .RS
 448 .PP
 449 \f[CB]MCMN\f[R]: Minimum metaspace capacity (KB).
 450 .PP
 451 \f[CB]MCMX\f[R]: Maximum metaspace capacity (KB).
 452 .PP
 453 \f[CB]MC\f[R]: Metaspace Committed Size (KB).
 454 .PP
 455 \f[CB]CCSMN\f[R]: Compressed class space minimum capacity (KB).
 456 .PP
 457 \f[CB]CCSMX\f[R]: Compressed class space maximum capacity (KB).
 458 .PP
 459 \f[CB]YGC\f[R]: Number of young generation GC events.
 460 .PP
 461 \f[CB]FGC\f[R]: Number of full GC events.
 462 .PP
 463 \f[CB]FGCT\f[R]: Full garbage collection time.
 464 .PP
 465 \f[CB]GCT\f[R]: Total garbage collection time.
 466 .RE
 467 .TP
 468 .B \f[CB]\-gcutil\f[R] \f[I]option\f[R]
 469 Summary of garbage collection statistics.
 470 .RS
 471 .PP
 472 \f[CB]S0\f[R]: Survivor space 0 utilization as a percentage of the
 473 space\[aq]s current capacity.
 474 .PP
 475 \f[CB]S1\f[R]: Survivor space 1 utilization as a percentage of the
 476 space\[aq]s current capacity.
 477 .PP
 478 \f[CB]E\f[R]: Eden space utilization as a percentage of the space\[aq]s
 479 current capacity.
 480 .PP
 481 \f[CB]O\f[R]: Old space utilization as a percentage of the space\[aq]s
 482 current capacity.
 483 .PP
 484 \f[CB]M\f[R]: Metaspace utilization as a percentage of the space\[aq]s
 485 current capacity.
 486 .PP
 487 \f[CB]CCS\f[R]: Compressed class space utilization as a percentage.
 488 .PP
 489 \f[CB]YGC\f[R]: Number of young generation GC events.
 490 .PP
 491 \f[CB]YGCT\f[R]: Young generation garbage collection time.
 492 .PP
 493 \f[CB]FGC\f[R]: Number of full GC events.
 494 .PP
 495 \f[CB]FGCT\f[R]: Full garbage collection time.
 496 .PP
 497 \f[CB]GCT\f[R]: Total garbage collection time.
 498 .RE
 499 .TP
 500 .B \f[CB]\-printcompilation\f[R] \f[I]option\f[R]
 501 Java HotSpot VM compiler method statistics.
 502 .RS
 503 .PP
 504 \f[CB]Compiled\f[R]: Number of compilation tasks performed by the most
 505 recently compiled method.
 506 .PP
 507 \f[CB]Size\f[R]: Number of bytes of byte code of the most recently
 508 compiled method.
 509 .PP
 510 \f[CB]Type\f[R]: Compilation type of the most recently compiled method.
 511 .PP
 512 \f[CB]Method\f[R]: Class name and method name identifying the most
 513 recently compiled method.
 514 Class name uses a slash (/) instead of a dot (.) as a name space
 515 separator.
 516 The method name is the method within the specified class.
 517 The format for these two fields is consistent with the HotSpot
 518 \f[CB]\-XX:+PrintCompilation\f[R] option.
 519 .RE
 520 .SH VIRTUAL MACHINE IDENTIFIER
 521 .PP
 522 The syntax of the \f[CB]vmid\f[R] string corresponds to the syntax of a
 523 URI:
 524 .RS
 525 .PP
 526 [\f[I]protocol\f[R]\f[CB]:\f[R]][\f[CB]//\f[R]]\f[I]lvmid\f[R][\f[CB]\@\f[R]\f[I]hostname\f[R][\f[CB]:\f[R]\f[I]port\f[R]][\f[CB]/\f[R]\f[I]servername\f[R]]
 527 .RE
 528 .PP
 529 The syntax of the \f[CB]vmid\f[R] string corresponds to the syntax of a
 530 URI.
 531 The \f[CB]vmid\f[R] string can vary from a simple integer that represents
 532 a local JVM to a more complex construction that specifies a
 533 communications protocol, port number, and other implementation\-specific
 534 values.
 535 .TP
 536 .B \f[I]protocol\f[R]
 537 The communications protocol.
 538 If the \f[I]protocol\f[R] value is omitted and a host name isn\[aq]t
 539 specified, then the default protocol is a platform\-specific optimized
 540 local protocol.
 541 If the \f[I]protocol\f[R] value is omitted and a host name is specified,
 542 then the default protocol is \f[CB]rmi\f[R].
 543 .RS
 544 .RE
 545 .TP
 546 .B \f[I]lvmid\f[R]
 547 The local virtual machine identifier for the target JVM.
 548 The \f[I]lvmid\f[R] is a platform\-specific value that uniquely
 549 identifies a JVM on a system.
 550 The \f[I]lvmid\f[R] is the only required component of a virtual machine
 551 identifier.
 552 The \f[I]lvmid\f[R] is typically, but not necessarily, the operating
 553 system\[aq]s process identifier for the target JVM process.
 554 You can use the \f[CB]jps\f[R] command to determine the \f[I]lvmid\f[R]
 555 provided the JVM processes is not running in a separate docker instance.
 556 You can also determine the \f[I]lvmid\f[R] on Oracle Solaris, Linux, and
 557 OS X platforms with the \f[CB]ps\f[R] command, and on Windows with the
 558 Windows Task Manager.
 559 .RS
 560 .PP
 561 \f[B]Note:\f[R] JDK 10 has added support for using the Attach API when
 562 attaching to Java processes running in a separate docker process.
 563 However, the \f[CB]jps\f[R] command will not list the JVM processes that
 564 are running in a separate docker instance.
 565 If you are trying to connect a Linux host with a Virtual Machine that is
 566 in a docker container, you must use tools such as \f[CB]ps\f[R] to look up
 567 the PID of the JVM.
 568 .RE
 569 .TP
 570 .B \f[I]hostname\f[R]
 571 A host name or IP address that indicates the target host.
 572 If the \f[I]hostname\f[R] value is omitted, then the target host is the
 573 local host.
 574 .RS
 575 .RE
 576 .TP
 577 .B \f[I]port\f[R]
 578 The default port for communicating with the remote server.
 579 If the \f[I]hostname\f[R] value is omitted or the \f[I]protocol\f[R] value
 580 specifies an optimized, local protocol, then the \f[I]port\f[R] value is
 581 ignored.
 582 Otherwise, treatment of the \f[I]port\f[R] parameter is
 583 implementation\-specific.
 584 For the default \f[CB]rmi\f[R] protocol, the port value indicates the port
 585 number for the \f[CB]rmiregistry\f[R] on the remote host.
 586 If the \f[I]port\f[R] value is omitted and the \f[I]protocol\f[R] value
 587 indicates \f[CB]rmi\f[R], then the default rmiregistry port (1099) is
 588 used.
 589 .RS
 590 .RE
 591 .TP
 592 .B \f[I]servername\f[R]
 593 The treatment of the \f[I]servername\f[R] parameter depends on
 594 implementation.
 595 For the optimized local protocol, this field is ignored.
 596 For the \f[CB]rmi\f[R] protocol, it represents the name of the RMI remote
 597 object on the remote host.
 598 .RS
 599 .RE
 600 .SH EXAMPLES
 601 .PP
 602 This section presents some examples of monitoring a local JVM with an
 603 \f[I]lvmid\f[R] of 21891.
 604 .SH THE GCUTIL OPTION
 605 .PP
 606 This example attaches to lvmid 21891 and takes 7 samples at 250
 607 millisecond intervals and displays the output as specified by the
 608 \f[CB]\-gcutil\f[R] option.
 609 .PP
 610 The output of this example shows that a young generation collection
 611 occurred between the third and fourth sample.
 612 The collection took 0.078 seconds and promoted objects from the eden
 613 space (E) to the old space (O), resulting in an increase of old space
 614 utilization from 66.80% to 68.19%.
 615 Before the collection, the survivor space was 97.02% utilized, but after
 616 this collection it\[aq]s 91.03% utilized.
 617 .IP
 618 .nf
 619 \f[CB]
 620 jstat\ \-gcutil\ 21891\ 250\ 7
 621 \ \ S0\ \ \ \ \ S1\ \ \ \ \ E\ \ \ \ \ \ O\ \ \ \ \ \ M\ \ \ \ \ CCS\ \ \ \ YGC\ \ \ \ \ YGCT\ \ \ \ FGC\ \ \ \ FGCT\ \ \ \ \ GCT
 622 \ \ 0.00\ \ 97.02\ \ 70.31\ \ 66.80\ \ 95.52\ \ 89.14\ \ \ \ \ \ 7\ \ \ \ 0.300\ \ \ \ \ 0\ \ \ \ 0.000\ \ \ \ 0.300
 623 \ \ 0.00\ \ 97.02\ \ 86.23\ \ 66.80\ \ 95.52\ \ 89.14\ \ \ \ \ \ 7\ \ \ \ 0.300\ \ \ \ \ 0\ \ \ \ 0.000\ \ \ \ 0.300
 624 \ \ 0.00\ \ 97.02\ \ 96.53\ \ 66.80\ \ 95.52\ \ 89.14\ \ \ \ \ \ 7\ \ \ \ 0.300\ \ \ \ \ 0\ \ \ \ 0.000\ \ \ \ 0.300
 625 \ 91.03\ \ \ 0.00\ \ \ 1.98\ \ 68.19\ \ 95.89\ \ 91.24\ \ \ \ \ \ 8\ \ \ \ 0.378\ \ \ \ \ 0\ \ \ \ 0.000\ \ \ \ 0.378
 626 \ 91.03\ \ \ 0.00\ \ 15.82\ \ 68.19\ \ 95.89\ \ 91.24\ \ \ \ \ \ 8\ \ \ \ 0.378\ \ \ \ \ 0\ \ \ \ 0.000\ \ \ \ 0.378
 627 \ 91.03\ \ \ 0.00\ \ 17.80\ \ 68.19\ \ 95.89\ \ 91.24\ \ \ \ \ \ 8\ \ \ \ 0.378\ \ \ \ \ 0\ \ \ \ 0.000\ \ \ \ 0.378
 628 \ 91.03\ \ \ 0.00\ \ 17.80\ \ 68.19\ \ 95.89\ \ 91.24\ \ \ \ \ \ 8\ \ \ \ 0.378\ \ \ \ \ 0\ \ \ \ 0.000\ \ \ \ 0.378
 629 \f[R]
 630 .fi
 631 .SH REPEAT THE COLUMN HEADER STRING
 632 .PP
 633 This example attaches to lvmid 21891 and takes samples at 250
 634 millisecond intervals and displays the output as specified by
 635 \f[CB]\-gcnew\f[R] option.
 636 In addition, it uses the \f[CB]\-h3\f[R] option to output the column
 637 header after every 3 lines of data.
 638 .PP
 639 In addition to showing the repeating header string, this example shows
 640 that between the second and third samples, a young GC occurred.
 641 Its duration was 0.001 seconds.
 642 The collection found enough active data that the survivor space 0
 643 utilization (S0U) would have exceeded the desired survivor size (DSS).
 644 As a result, objects were promoted to the old generation (not visible in
 645 this output), and the tenuring threshold (TT) was lowered from 31 to 2.
 646 .PP
 647 Another collection occurs between the fifth and sixth samples.
 648 This collection found very few survivors and returned the tenuring
 649 threshold to 31.
 650 .IP
 651 .nf
 652 \f[CB]
 653 jstat\ \-gcnew\ \-h3\ 21891\ 250
 654 \ S0C\ \ \ \ S1C\ \ \ \ S0U\ \ \ \ S1U\ \ \ TT\ MTT\ \ DSS\ \ \ \ \ \ EC\ \ \ \ \ \ \ EU\ \ \ \ \ YGC\ \ \ \ \ YGCT
 655 \ \ 64.0\ \ \ 64.0\ \ \ \ 0.0\ \ \ 31.7\ 31\ \ 31\ \ \ 32.0\ \ \ \ 512.0\ \ \ \ 178.6\ \ \ \ 249\ \ \ \ 0.203
 656 \ \ 64.0\ \ \ 64.0\ \ \ \ 0.0\ \ \ 31.7\ 31\ \ 31\ \ \ 32.0\ \ \ \ 512.0\ \ \ \ 355.5\ \ \ \ 249\ \ \ \ 0.203
 657 \ \ 64.0\ \ \ 64.0\ \ \ 35.4\ \ \ \ 0.0\ \ 2\ \ 31\ \ \ 32.0\ \ \ \ 512.0\ \ \ \ \ 21.9\ \ \ \ 250\ \ \ \ 0.204
 658 \ S0C\ \ \ \ S1C\ \ \ \ S0U\ \ \ \ S1U\ \ \ TT\ MTT\ \ DSS\ \ \ \ \ \ EC\ \ \ \ \ \ \ EU\ \ \ \ \ YGC\ \ \ \ \ YGCT
 659 \ \ 64.0\ \ \ 64.0\ \ \ 35.4\ \ \ \ 0.0\ \ 2\ \ 31\ \ \ 32.0\ \ \ \ 512.0\ \ \ \ 245.9\ \ \ \ 250\ \ \ \ 0.204
 660 \ \ 64.0\ \ \ 64.0\ \ \ 35.4\ \ \ \ 0.0\ \ 2\ \ 31\ \ \ 32.0\ \ \ \ 512.0\ \ \ \ 421.1\ \ \ \ 250\ \ \ \ 0.204
 661 \ \ 64.0\ \ \ 64.0\ \ \ \ 0.0\ \ \ 19.0\ 31\ \ 31\ \ \ 32.0\ \ \ \ 512.0\ \ \ \ \ 84.4\ \ \ \ 251\ \ \ \ 0.204
 662 \ S0C\ \ \ \ S1C\ \ \ \ S0U\ \ \ \ S1U\ \ \ TT\ MTT\ \ DSS\ \ \ \ \ \ EC\ \ \ \ \ \ \ EU\ \ \ \ \ YGC\ \ \ \ \ YGCT
 663 \ \ 64.0\ \ \ 64.0\ \ \ \ 0.0\ \ \ 19.0\ 31\ \ 31\ \ \ 32.0\ \ \ \ 512.0\ \ \ \ 306.7\ \ \ \ 251\ \ \ \ 0.204
 664 \f[R]
 665 .fi
 666 .SH INCLUDE A TIME STAMP FOR EACH SAMPLE
 667 .PP
 668 This example attaches to lvmid 21891 and takes 3 samples at 250
 669 millisecond intervals.
 670 The \f[CB]\-t\f[R] option is used to generate a time stamp for each sample
 671 in the first column.
 672 .PP
 673 The Timestamp column reports the elapsed time in seconds since the start
 674 of the target JVM.
 675 In addition, the \f[CB]\-gcoldcapacity\f[R] output shows the old
 676 generation capacity (OGC) and the old space capacity (OC) increasing as
 677 the heap expands to meet allocation or promotion demands.
 678 The old generation capacity (OGC) has grown from 11,696 KB to 13,820 KB
 679 after the eighty\-first full garbage collection (FGC).
 680 The maximum capacity of the generation (and space) is 60,544 KB (OGCMX),
 681 so it still has room to expand.
 682 .IP
 683 .nf
 684 \f[CB]
 685 Timestamp\ \ \ \ \ \ OGCMN\ \ \ \ OGCMX\ \ \ \ \ OGC\ \ \ \ \ \ \ OC\ \ \ \ \ \ \ YGC\ \ \ FGC\ \ \ \ FGCT\ \ \ \ GCT
 686 \ \ \ \ \ \ \ \ \ \ 150.1\ \ \ 1408.0\ \ 60544.0\ \ 11696.0\ \ 11696.0\ \ \ 194\ \ \ \ 80\ \ \ \ 2.874\ \ \ 3.799
 687 \ \ \ \ \ \ \ \ \ \ 150.4\ \ \ 1408.0\ \ 60544.0\ \ 13820.0\ \ 13820.0\ \ \ 194\ \ \ \ 81\ \ \ \ 2.938\ \ \ 3.863
 688 \ \ \ \ \ \ \ \ \ \ 150.7\ \ \ 1408.0\ \ 60544.0\ \ 13820.0\ \ 13820.0\ \ \ 194\ \ \ \ 81\ \ \ \ 2.938\ \ \ 3.863
 689 \f[R]
 690 .fi
 691 .SH MONITOR INSTRUMENTATION FOR A REMOTE JVM
 692 .PP
 693 This example attaches to lvmid 40496 on the system named
 694 \f[CB]remote.domain\f[R] using the \f[CB]\-gcutil\f[R] option, with samples
 695 taken every second indefinitely.
 696 .PP
 697 The lvmid is combined with the name of the remote host to construct a
 698 vmid of \f[CB]40496\@remote.domain\f[R].
 699 This vmid results in the use of the \f[CB]rmi\f[R] protocol to communicate
 700 to the default \f[CB]jstatd\f[R] server on the remote host.
 701 The \f[CB]jstatd\f[R] server is located using the \f[CB]rmiregistry\f[R]
 702 command on \f[CB]remote.domain\f[R] that\[aq]s bound to the default port
 703 of the \f[CB]rmiregistry\f[R] command (port 1099).
 704 .IP
 705 .nf
 706 \f[CB]
 707 jstat\ \-gcutil\ 40496\@remote.domain\ 1000
 708 \&...\ output\ omitted
 709 \f[R]
 710 .fi