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jstat(1)                                                              jstat(1)




NAME

       jstat - Java Virtual Machine statistics monitoring tool


SYNOPSIS

       jstat  [ generalOption | outputOptions vmid [ interval [ s|ms ] [ count
       ] ] ]


DESCRIPTION

       The jstat tool displays  performance  statistics  for  an  instrumented
       HotSpot Java virtual machine (JVM). The target JVM is identified by its
       virtual machine identifier, or vmid option described below.

       NOTE - This utility is unsupported and may or may not be  available  in
       future versions of the J2SE SDK.  It is currently not available on Win-
       dows 98 and Windows ME platforms.

   VIRTUAL MACHINE IDENTIFIER
       The syntax of the vmid string largely corresponds to the  syntax  of  a
       URI:

              [protocol:][//]lvmid[@hostname][:port][/servername]

       protocol       The  communications protocol. If the protocol is omitted
                      and a hostname is not specified, the default protocol is
                      a  platform  specific  optimized  local protocol. If the
                      protocol is omitted and a hostname  is  specified,  then
                      the default protocol is rmi.

       lvmid          The local virtual machine identifier for the target JVM.
                      The lvmid is a  platform-specific  value  that  uniquely
                      identifies  a  JVM  on  a  system. The lvmid is the only
                      required component of a virtual machine identifier.  The
                      lvmid  is  typically, but not necessarily, the operating
                      system's process identifier for the target JVM  process.
                      You  can  use  the  jps  command to determine the lvmid.
                      Also, you can determine lvmid on Unix platforms with the
                      ps  command,  and  on Windows with the Windows Task Man-
                      ager.

       hostname       A hostname or IP address indicating the target host.  If
                      hostname  is  omitted, then the target host is the local
                      host.

       port           The default  port  for  communicating  with  the  remote
                      server. If the hostname is omitted or the protocol spec-
                      ifies  an  optimized,  local  protocol,  then  port   is
                      ignored.  Otherwise,  treatment of the port parameter is
                      implementation specific. For the default  rmi  protocol,
                      the  port  indicates the port number for the rmiregistry
                      on the remote host. If port  is  omitted,  and  protocol
                      indicates  rmi, then the default rmiregistry port (1099)
                      is used.

       servername     The treatment of this parameter depends  on  implementa-
                      tion.  For  the  optimized local protocol, this field is
                      ignored. For the rmi protocol, it represents the name of
                      the RMI remote object on the remote host.


PARAMETERS

       generalOption  A  single  general command-line option (-help, -options,
                      or -version)

       outputOptions  One or more  output  options,  consisting  of  a  single
                      statOption, plus any of the -t, -h, and -J options.

       vmid           Virtual machine identifier, a string indicating the tar-
                      get Java virtual machine (JVM). The general syntax is

              [protocol:][//]lvmid[@hostname[:port]/servername

       The syntax of the vmid string largely corresponds to the  syntax  of  a
       URI.  The  vmid can vary from a simple integer representing a local JVM
       to a more complex construction specifying  a  communications  protocol,
       port  number,  and  other  implementation-specific  values. See Virtual
       Machine Identifier below for details.

       interval[s|ms] Sampling interval in the specified units, seconds (s) or
                      milliseconds (ms). Default units are milliseconds.  Must
                      be a positive integer.  If specified, jstat will produce
                      its output at each interval.

       count          Number of samples to display. Default value is infinity;
                      that is, jstat displays statistics until the target  JVM
                      terminates  or the jstat command is terminated.  Must be
                      a positive integer.


OPTIONS

       The jstat command supports two types of options,  general  options  and
       output  options.   General  options cause jstat to display simple usage
       and version information. Output options determine the content and  for-
       mat of the statistical output.

       NOTE-  All  options,  and  their functionality are subject to change or
       removal in future releases.

   GENERAL OPTIONS
       If you specify one of the general options, you cannot specify any other
       option or parameter.

       -help          Display help message.

       -version       Display version information.

       -options       Display  list  of  statistics  options.  See  the Output
                      Options section below.

   OUTPUT OPTIONS
       If you do not specify a general option, then  you  can  specify  output
       options.   Output  options  determine the content and format of jstat's
       output, and consist of a single statOption, plus any of the other  out-
       put options (-h, -t, and -J).  The statOption must come first.

       Output  is  formatted as a table, with columns are separated by spaces.
       A header row with titles describes the columns.  Use the -h  option  to
       set  the  frequency  at  which  the header is displayed.  Column header
       names are generally consistent between the different options.  In  gen-
       eral, if two options provide a column with the same name, then the data
       source for the two columns are the same.

       Use the -t 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 startup of the target JVM.  The  resolution  of
       the time stamp is dependent on various factors and is subject to varia-
       tion due to delayed thread scheduling on heavily loaded systems.

       Use the interval and count parameters to determine how  frequently  and
       how many times, respectively, jstat displays its output.

       NOTE-  You  are  advised  not  to write scripts to parse jstat's output
       since the format may change in future releases. If you choose to  write
       scripts  that  parse  jstat  output,  expect  to modify them for future
       releases of this tool.

       -statOption    Determines the statistics information  that  jstat  dis-
                      plays.  The following table lists the available options.
                      Use the -options general option to display the  list  of
                      options for a particular platform installation.



      +-----------------+------------------------------------------------------+
      |     Option      |                     Displays...                      |
      +-----------------+------------------------------------------------------+
      |class            | Statistics on the behavior of the class loader       |
      |compiler         | Statistics  on  the behavior of the HotSpot Just-In- |
      |                 | Time compiler                                        |
      |gc               | Statistics on the behavior of the garbage  collected |
      |                 | heap                                                 |
      |gccapacity       | Statistics  of the capacities of the generations and |
      |                 | their corresponding spaces.                          |
      |gccause          | Summary of garbage collection  statistics  (same  as |
      |                 | -gcutil), with the cause of the last and current (if |
      |                 | applicable) garbage collection events.               |
      |gcnew            | Statistics of the behavior of the new generation.    |
      |gcnewcapacity    | Statistics of the sizes of the new  generations  and |
      |                 | its corresponding spaces.                            |
      |gcold            | Statistics  of the behavior of the old and permanent |
      |                 | generations.                                         |
      |gcoldcapacity    | Statistics of the sizes of the old generation.       |
      |gcpermcapacity   | Statistics of the sizes of the permanent generation. |
      |gcutil           | Summary of garbage collection statistics.            |
      |printcompilation | Summary of garbage collection statistics.            |
      +-----------------+------------------------------------------------------+
       -h n           Display a column header every n samples  (output  rows),
                      where n is a positive integer. Default value is 0, which
                      displays the column header above the first row of  data.

       -t n           Display  a  timestamp column as the first column of out-
                      put. The timestamp is the the time since the start  time
                      of the target JVM.

       -JjavaOption   Pass  javaOption  to  the java application launcher. For
                      example,  -J-Xms48m  sets  the  startup  memory  to   48
                      megabytes.  For a complete list of options, see java(1).

   STATOPTIONS AND OUTPUT
       The following tables summarize the columns that jstat outputs for  each
       statOption.

       class  Class Loader Statistics



         +---------+--------------------------------------------------------+
         | Column  |                      Description                       |
         +---------+--------------------------------------------------------+
         |Loaded   | Number of classes loaded                               |
         |Bytes    | Number of Kbytes loaded                                |
         |Unloaded | Number of classes unloaded                             |
         |Bytes    | Number of Kbytes unloaded                              |
         |Time     | Time spent performing class load and unload operations |
         +---------+--------------------------------------------------------+
       compiler
              HotSpot Just-In-Time Compiler Statistics



       +-------------+-------------------------------------------------------+
       |   Column    |                      Description                      |
       +-------------+-------------------------------------------------------+
       |Compiled     | Humber of compilation tasks performed                 |
       |Failed       | Number of compilation tasks that failed               |
       |Invalid      | Number of compilation tasks that were invalidated     |
       |Time         | Time spent performing compilation tasks               |
       |FailedType   | Compile type of the last failed compilation           |
       |FailedMethod | Class name and method for the last failed compilation |
       +-------------+-------------------------------------------------------+
       gc     Garbage-collected heap statistics



                +-------+-------------------------------------------+
                |Column |                Description                |
                +-------+-------------------------------------------+
                |SOC    | Current survivor space 0 capacity (KB).   |
                |S1C    | Current survivor space 1 capacity (KB).   |
                |S0U    | Survivor space 0 utilization (KB).        |
                |S1U    | Survivor space 1 utilization (KB).        |
                |EC     | Current eden space capacity (KB).         |
                |EU     | Eden space utilization (KB).              |
                |OC     | Current old space capacity (KB).          |
                |OU     | Old space utilization (KB).               |
                |PC     | Current permanent space capacity (KB).    |
                |PU     | Permanent space utilization (KB).         |
                |YGC    | Number of young generation GC Events.     |
                |YGCT   | Young generation garbage collection time. |
                |FGC    | Number of full GC events.                 |
                |FGCT   | Full garbage collection time.             |
                |GCT    | Total garbage collection time.            |
                +-------+-------------------------------------------+
       gccapacity
              Memory Pool Generation and Space Capacities



               +-------+---------------------------------------------+
               |Column |                 Description                 |
               +-------+---------------------------------------------+
               |NGCMN  | Minimum new generation capacity (KB).       |
               |NGCMX  | Maximum new generation capacity (KB).       |
               |NGC    | Current new generation capacity (KB).       |
               |S0C    | Current survivor space 0 capacity (KB).     |
               |S1C    | Current survivor space 1 capacity (KB).     |
               |EC     | Current eden space capacity (KB).           |
               |OGCMN  | Minimum old generation capacity (KB).       |
               |OGCMX  | Maximum old generation capacity (KB).       |
               |OGC    | Current old generation capacity (KB).       |
               |OC     | Current old space capacity (KB).            |
               |PGCMN  | Minimum permanent generation capacity (KB). |
               |PGCMX  | Maximum Permanent generation capacity (KB). |
               |PGC    | Current Permanent generation capacity (KB). |
               |PC     | Current Permanent space capacity (KB).      |
               |VGC    | Number of Young generation GC Events.       |
               |FGC    | Number of Full GC Events.                   |
               +-------+---------------------------------------------+
       gccause
              This option displays the same summary of garbage collection sta-
              tistics as the -gcutil option, but includes the  causes  of  the
              last  garbage  collection  event and (if applicable) the current
              garbage collection event. In addition to the columns listed  for
              -gcutil, this option adds the following columns:



                   +-------+--------------------------------------+
                   |Column |             Description              |
                   +-------+--------------------------------------+
                   |LGCC   | Cause of last Garbage Collection.    |
                   |GCC    | Cause of current Garbage Collection. |
                   +-------+--------------------------------------+
       gcnew  New Generation Statistics



                +-------+-------------------------------------------+
                |Column |                Description                |
                +-------+-------------------------------------------+
                |SOC    | Current survivor space 0 capacity (KB).   |
                |S1C    | Current survivor space 1 capacity (KB).   |
                |S0U    | Survivor space 0 utilization (KB).        |
                |S1U    | Survivor space 1 utilization (KB).        |
                |TT     | Tenuring threshold.                       |
                |MTT    | Maximum tenuring threshold.               |
                |DSS    | Desired survivor size (KB).               |
                |EC     | Current eden space capacity (KB).         |
                |EU     | Eden space utilization (KB).              |
                |VGC    | Number of young generation GC events.     |
                |VGCT   | Young generation garbage collection time. |
                +-------+-------------------------------------------+
       gcnewcapacity
              New Generation Space Size Statistics



                 +-------+-----------------------------------------+
                 |Column |               Description               |
                 +-------+-----------------------------------------+
                 |NGCMN  | Minimum new generation capacity (KB).   |
                 |NGCMX  | Maximum new generation capacity (KB).   |
                 |NGC    | Current new generation capacity (KB).   |
                 |S0CMX  | Maximum survivor space 0 capacity (KB). |
                 |S0C    | Current survivor space 0 capacity (KB). |
                 |S1CMX  | Maximum survivor space 1 capacity (KB). |
                 |S1C    | Current survivor space 1 capacity (KB). |
                 |ECMX   | Maximum eden space capacity (KB).       |
                 |EC     | Current eden space capacity (KB).       |
                 |YGC    | Number of young generation GC events.   |
                 |FGC    | Number of Full GC Events.               |
                 +-------+-----------------------------------------+
       gcold  Old and Permanent Generation Statistics



                  +-------+----------------------------------------+
                  |Column |              Description               |
                  +-------+----------------------------------------+
                  |PC     | Current permanent space capacity (KB). |
                  |PU     | Permanent space utilization (KB).      |
                  |OC     | Current old space capacity (KB).       |
                  |OU     | Old space utilization (KB).            |
                  |YGC    | Number of young generation GC events.  |
                  |FGC    | Number of Full GC events.              |
                  |FGCT   | Full garbage collection time.          |
                  |GCT    | Total garbage collection time.         |
                  +-------+----------------------------------------+
       gcoldcapacity
              Old Generation Statistics



                  +-------+---------------------------------------+
                  |Column |              Description              |
                  +-------+---------------------------------------+
                  |OGCMN  | Minimum old generation capacity (KB). |
                  |OGCMV  | Maximum old generation capacity (KB). |
                  |OGC    | Current old generation capacity (KB). |
                  |OC     | Current old space capacity (KB).      |
                  |YGC    | Number of young generation GC events. |
                  |FGC    | Number of Full GC events.             |
                  |FGCT   | Full garbage collection time.         |
                  |GCT    | Total garbage collection time.        |
                  +-------+---------------------------------------+
       gcpermcapacity
              Permanent Generation Statistics



               +-------+---------------------------------------------+
               |Column |                 Description                 |
               +-------+---------------------------------------------+
               |PGCMN  | Minimum permanent generation capacity (KB). |
               |PGCMX  | Maximum permanent generation capacity (KB). |
               |PGC    | Current permanent generation capacity (KB). |
               |PC     | Current permanent space capacity (KB).      |
               |YGC    | Number of young generation GC events.       |
               |FGC    | Number of Full GC events.                   |
               |FGCT   | Full garbage collection time.               |
               |GCT    | Total garbage collection time.              |
               +-------+---------------------------------------------+
       gcutil Summary of Garbage Collection Statistics



                +-------+-------------------------------------------+
                |Column |                Description                |
                +-------+-------------------------------------------+
                |S0     | Survivor  space  0  utilization as a per- |
                |       | centage of the space's current  capacity. |
                |S1     | Survivor  space  1  utilization as a per- |
                |       | centage of the space's current  capacity. |
                |E      | Eden space utilization as a percentage of |
                |       | the space's current capacity.             |
                |O      | Old space utilization as a percentage  of |
                |       | the space's current capacity.             |
                |P      | Permanent space utilization as a percent- |
                |       | age of the space's current capacity.      |
                |YGC    | Number of young generation GC events.     |
                |YGCT   | Young generation garbage collection time. |
                |FGC    | Number of Full GC events.                 |
                |FGCT   | Full garbage collection time.             |
                |GCT    | Total garbage collection time.            |
                +-------+-------------------------------------------+
       printcompilation
              HotSpot Compiler Method Statistics



              +---------+---------------------------------------------+
              | Column  |                 Description                 |
              +---------+---------------------------------------------+
              |Compiled | Number of compilation tasks performed.      |
              |Size     | Number of bytes of bytecode for the method. |
              |Type     | Compilation type.                           |
              |Method   | Class name and method name identifying  the |
              |         | compiled   method.   Class  name  uses  "/" |
              |         | instead  of  "."  as  namespace  separator. |
              |         | Method  name is the method within the given |
              |         | class. The format for these two  fields  is |
              |         | consistent with the HotSpot - XX:+PrintCom- |
              |         | plation option.                             |
              +---------+---------------------------------------------+


EXAMPLES

       This section presents some examples of monitoring a local  JVM  with  a
       lvmid of 21891.

   Using the gcutil option
       This  example  attaches  to lvmid 21891 and takes 7 samples at 250 mil-
       lisecond intervals and displays the output as specified by the  -gcutil
       option.

       jstat -gcutil 21891 250 7
         S0     S1     E      O      P     YGC    YGCT    FGC    FGCT     GCT
        12.44   0.00  27.20   9.49  96.70    78    0.176     5    0.495    0.672
        12.44   0.00  62.16   9.49  96.70    78    0.176     5    0.495    0.672
        12.44   0.00  83.97   9.49  96.70    78    0.176     5    0.495    0.672
         0.00   7.74   0.00   9.51  96.70    79    0.177     5    0.495    0.673
         0.00   7.74  23.37   9.51  96.70    79    0.177     5    0.495    0.673
         0.00   7.74  43.82   9.51  96.70    79    0.177     5    0.495    0.673
         0.00   7.74  58.11   9.51  96.71    79    0.177     5    0.495    0.673

       The  output  of  this  example shows that a young generation collection
       occurred between the 3rd and 4th sample. The collection took 0.001 sec-
       onds 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.

   Repeating the column header string
       This example attaches to lvmid 21891 and takes samples at 250 millisec-
       ond  intervals  and displays the output as specified by -gcutil option.
       In addition, it uses the -h3 option to output the column  header  after
       every 3 lines of data.

       jstat -gcnew -h3 21891 250
        S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT
         64.0   64.0    0.0   31.7 31  31   32.0    512.0    178.6    249    0.203
         64.0   64.0    0.0   31.7 31  31   32.0    512.0    355.5    249    0.203
         64.0   64.0   35.4    0.0  2  31   32.0    512.0     21.9    250    0.204
        S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT
         64.0   64.0   35.4    0.0  2  31   32.0    512.0    245.9    250    0.204
         64.0   64.0   35.4    0.0  2  31   32.0    512.0    421.1    250    0.204
         64.0   64.0    0.0   19.0 31  31   32.0    512.0     84.4    251    0.204
        S0C    S1C    S0U    S1U   TT MTT  DSS      EC       EU     YGC     YGCT
         64.0   64.0    0.0   19.0 31  31   32.0    512.0    306.7    251    0.204

       In  addition to showing the repeating header string, this example shows
       that between the 2nd and 3rd samples, a young GC occurred. Its duration
       was  0.001 seconds. The collection found enough live data that the sur-
       vivor space 0 utilization (S0U) would would have exceeded  the  desired
       survivor Size (DSS). As a result, objects were promoted to the old gen-
       eration (not visible in this output), and the tenuring  threshold  (TT)
       was lowered from 31 to 2.

       Another collection occurs between the 5th and 6th samples. This collec-
       tion found very few survivors and returned the  tenuring  threshold  to
       31.

   Including a time stamp for each sample
       This  example  attaches  to lvmid 21891 and takes 3 samples at 250 mil-
       lisecond intervals. The -t option is used to generate a time stamp  for
       each sample in the first column.

       jstat -gcoldcapacity -t 21891 250 3
       Timestamp  OGCMN    OGCMX    OGC      OC       YGC   FGC   FGCT    GCT
       150.1      1408.0   60544.0  11696.0  11696.0  194   80    2.874   3.799
       150.4      1408.0   60544.0  13820.0  13820.0  194   81    2.938   3.863
       150.7      1408.0   60544.0  13820.0  13820.0  194   81    2.938   3.863

   Monitor instrumentation for a remote JVM
       This  example attaches to lvmid 40496 on the system named remote.domain
       using the -gcutil option, with samples taken every second indefinitely.

       jstat -gcutil 40496@remote.domain 1000
        ... output omitted

       The  lvmid  is combined with the name of the remote host to construct a
       vmid of 40496@remote.domain. This vmid results in the use  of  the  rmi
       protocol  to  communicate  to  the  default jstatd server on the remote
       host.  The  jstatd  server  is  located  using   the   rmiregistry   on
       remote.domain  that  is  bound  to  the  default rmiregistry port (port
       1099).


SEE ALSO

       java(1) jps(1) jstatd(1) rmiregistry(1)



                                 13 June 2004                         jstat(1)

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