jstat(1)                   OpenBSD Reference Manual                   jstat(1)



NAME
       jstat - Java Virtual Machine Statistics Monitoring Tool

SYNOPSIS
       jstat [ generalOption | outputOptionsvmid [interval[s|ms] [count]] ]

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 target 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 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.

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 not be available in future
       versions of the JDK. It is not currently available on Windows 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 Manager.

       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 specifies 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 implementation. 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.

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 format 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
       output 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 general, 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
       variation 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 displays. 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 of the behavior
                             of the HotSpot
                             Just-in-Time compiler.
          gc                 Statistics of 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   HotSpot compilation method
                             statistics.

       -hn
          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.

       -tn
          Display a timestamp column as the first column of output. 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 the following documents:

          * java - the Java application launcher (Solaris) @
            http://java.sun.com/javase/6/docs/technotes/tools/solaris/java.html

          * java - the Java application launcher (Bsd) @
            http://java.sun.com/javase/6/docs/technotes/tools/bsd/java.html

          * java - the Java application launcher (Windows)

   STATOPTIONS AND
       OUTPUT

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

   -class Option
       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
       Option

       HotSpot Just-In-Time Compiler Statistics
       Column                                     Description
       Compiled                                   Number 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 Option
       Garbage-collected heap statistics
       Column                              Description
       S0C                                 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 Option
       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).
       YGC                                           Number of Young generation
                                                     GC Events.
       FGC                                           Number of Full GC Events.

   -gccause
       Option

       This option displays the same summary of garbage collection statistics
       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:

       Garbage Collection Statistics, Including GC Events
       Column                                               Description
       LGCC                                                 Cause of last Garbage
                                                            Collection.
       GCC                                                  Cause of current Garbage
                                                            Collection.

   -gcnew Option
       New Generation Statistics
       Column                      Description
       S0C                         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).
       YGC                         Number of young generation
                                   GC events.
       YGCT                        Young generation garbage
                                   collection time.

   -gcnewcapacity Option
       New Generation Space Size Statistics
       Column                                 Description
       NGCMN         T}~T{ 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 Option
       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 Option
       Old Generation Statistics
       Column                      Description
       OGCMN                       Minimum old generation
                                   capacity (KB).
       OGCMX                       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 Option
       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
       Option

       Summary of Garbage Collection Statistics
       Column                                     Description
       S0                                         Survivor space 0
                                                  utilization as a
                                                  percentage of the space's
                                                  current capacity.
       S1                                         Survivor space 1
                                                  utilization as a
                                                  percentage 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
                                                  percentage 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 Option
       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:+PrintComplation
                                            option.



       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
       millisecond 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
       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.

   Repeating the column header
       string

       This example attaches to lvmid 21891 and takes samples at 250
       millisecond 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
       survivor space 0 utilization (S0U) would 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.

       Another collection occurs between the 5th and 6th samples. This
       collection 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
       millisecond 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

       The Timestamp column reports the elapsed time in seconds since the
       start of the target JVM. In addition, the -gcoldcapacity output shows
       the old generation capacity (OGC) and the old space capacity (OC)
       increasing as the heap expands to meet allocation and/or promotion
       demands. The old generation capacity (OGC) has grown to from 11696 KB
       to 13820 KB after the 81st Full GC (FGC). The maximum capacity of the
       generation (and space) is 60544 KB (OGCMX), so it still has room to
       expand.

   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


       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 - the Java Application Launcher

          * jps - the Java Process Status Application

          * jstatd - the jvmstat daemon

          * rmiregistry - the Java Remote Object Registry




                                  06 Aug 2006                         jstat(1)
