docs/troubleshooting-guide/src/main/asciidoc/overview.adoc - glassfish - Git at Google

 type=page
 status=published
 title=Overview of {productName} Troubleshooting
 next=specific-issues.html
 prev=preface.html
 ~~~~~~

 = Overview of {productName} Troubleshooting

 [[GSTSG00002]][[abgap]]


 [[overview-of-glassfish-server-open-source-edition-troubleshooting]]
 == 1 Overview of {productName} Troubleshooting

 This chapter describes some of the tools, methods, and resources
 available for troubleshooting {productName}.
 Guidelines for evaluating and investigating a problem are provided.

 This chapter contains the following sections:

 * link:#abgar[Identifying the Problem]
 * link:#ghuvy[Troubleshooting Tools]
 * link:#ghuyv[Where to Go for More Information]

 [[abgar]][[GSTSG00039]][[identifying-the-problem]]

 === Identifying the Problem

 Application servers are typically deployed in complex operating
 environments and involve many technologies, products, and tools.
 Understanding and diagnosing problems in enterprise software with many
 components performing many tasks can be a challenge. This section
 describes how to get started , and contains the following topics:

 * link:#ghvay[First Steps]
 * link:#ghuvf[Gathering Information]
 * link:#abgax[Examining Log Files]
 * link:#ghuvd[Monitoring the System]

 [[ghvay]][[GSTSG00171]][[first-steps]]

 ==== First Steps

 Sometimes the most obvious solutions are overlooked. As you begin your
 investigation, try the following steps first.

 [[ghyku]][[GSTSG00077]][[verify-system-requirements-and-configuration]]

 ===== Verify System Requirements and Configuration

 Ensure that your system meets the requirements listed in
 "link:release-notes/release-notes.html#GSRLN00131[Hardware and Software Requirements]"
 in {productName} Release Notes.
 Problems are likely to arise if you attempt to install on a platform that
 is not supported or on a system that in some other way does not meet release requirements.
 Also see "link:release-notes/release-notes.html#GSRLN00253[Known Issues]"
 in {productName} Release Notes for known issues related to installation.

 {productName} requires JDK release 6. The minimum
 (and certified) version of the JDK that is required for {productName} depends on the operating system:

 * For supported operating systems except Mac OS, the minimum required version is 1.6.0_17.
 * For the Mac OS X operating system, the minimum required version is 1.6.0_15.

 If necessary, download and install the required JDK software.

 On Solaris, Linux, and Windows systems, JDK software is available from the
 http://www.oracle.com/technetwork/java/javase/downloads/index.html[
 Java SE downloads page]
 (`http://www.oracle.com/technetwork/java/javase/downloads/index.html`).

 For Mac OS X systems, {productName} uses the JDK
 that is part of the Macintosh operating system. If necessary, obtain the
 required JDK version from the http://support.apple.com/downloads/[Mac OS
 X Updates site] (`http://support.apple.com/downloads/`).

 Also ensure that the `JAVA_HOME` environment variable on your system
 points to the JDK installation directory and not the Java Runtime
 Environment (JRE) software.

 Set `JAVA_HOME` and `$JAVA_HOME/bin` in the `PATH` to point to the
 supported JDK version.

 [[ghyml]][[GSTSG00078]][[review-known-issues]]

 ===== Review Known Issues

 Your problem might be related to a known issue for the release. Refer to
 the link:release-notes.html#GSRLN[{productName} Release Notes] for
 the latest information regarding known issues and possible workarounds.
 Also search the GlassFish Issue Tracker at
 `http://java.net/jira/browse/GLASSFISH`.

 [[ghykl]][[GSTSG00079]][[search-the-product-documentation]]

 ===== Search the Product Documentation

 {productName} includes complete product
 documentation. Search the documentation to see if your problem is
 addressed. See link:preface.html#ghpbz[{productName} Documentation
 Set] for the books in the documentation set and a description of their
 contents. Also see the Administration Console online help for detailed
 information about performing administrative tasks using the graphical
 interface.

 The following books will be especially helpful for troubleshooting:

 * link:release-notes.html#GSRLN[{productName} Release Notes],
   which provides the latest information regarding known issues and possible workarounds.
 * link:error-messages-reference.html#GSEMR[
   {productName} Error Message Reference],
   which lists error messages you might encounter when using {productName}.

 Use the product documentation to learn more about {productName}. The more you know about the product the easier it might
 be to figure out why something isn't working.

 [[ghymp]][[GSTSG00080]][[search-the-glassfish-mailing-lists-and-forums]]

 ===== Search the GlassFish Mailing Lists and Forums

 Lists and forums are extremely helpful resources, and are accessed as follows:

 * GlassFish mailing lists (start with users@glassfish.java.net and
   search the archives): `http://java.net/projects/glassfish/lists/`
 * GlassFish user forum: `http://www.java.net/forums/glassfish/glassfish`

 [[ghuvf]][[GSTSG00172]][[gathering-information]]

 ==== Gathering Information

 Troubleshooting and analysis require information. The more information
 you have the easier it is to classify a problem and search for its
 solution. Detailed information will also be necessary should you need to
 contact others for support, either through a community mailing list or
 through more formal Sun support channels.

 As you continue your investigation, consider the following questions.

 [[ghvar]][[GSTSG00081]][[when-does-the-problem-occur]]

 ===== When Does the Problem Occur?

 * What do the logs show? What kind of error message are you getting? For
 more information about logs, see link:#abgax[Examining Log Files]. Logs
 are a good place to start your troubleshooting.
 * What are you trying to do when the problem occurs and how are you
 doing it? What is the sequence of events?
 * Does the problem occur every time you perform the same type of
 operation, or does it seem random? Can you reproduce the issue?
 * Have other events or problems occurred that could possibly be related,
 such as web sessions closing early, exceptions being thrown in your own
 application logic, components not being correctly deployed or
 undeployed?

 [[ghvbb]][[GSTSG00082]][[what-is-your-environment]]

 ===== What Is Your Environment?

 * What version of {productName} are you using?
 What operating system and version? What JDK version? Many problems are
 caused simply because system requirements for the release are not met.
 Refer to the link:release-notes.html#GSRLN[{productName} Release
 Notes] for the latest information regarding system requirements, and
 make sure your system meets those requirements.
 * What resources does your system have, such as memory, disk, and swap
 space? If system memory is an issue, look for ways to optimize your
 configuration and consider taking other actions such as adding memory or
 decreasing system load.
 * Have any patches been applied? If so, what are the product and
 operating system patch numbers?
 * What other products and technologies are installed and being used in
 the installation?
 * How many application servers, web servers, and directory servers are
 installed? What are the products and versions?
 * How is the web server connected to {productName}? On the same system?
 * How is {productName} connected to the directory
 server?
 * What JDBC driver is being used to access the database?

 [[ghvce]][[GSTSG00083]][[what-is-your-system-configuration]]

 ===== What Is Your System Configuration?

 * What are your settings?
 * On which port is {productName} configured — the
 default or something else?
 * What defaults were changed during installation and what are the
 values?
 * What other settings were changed from the defaults and what are their
 values?
 * What are the parameters related to JVM heap, stack, and garbage
 collection set to?
 * What are the JVM options?
 * What is the permgen size? `OutOfMemoryError:PermGen space` errors are
 common and indicate that you need to increase the permanent generation
 space available.
 * Is SSL enabled?
 * What are your network settings (proxy, firewall, and so on)? What
 happens if you disable your firewall and attempt the task?

 [[ghvcr]][[GSTSG00084]][[what-is-different]]

 ===== What Is Different?

 * What is different that could have provoked the problem or triggered
 the event? Was something new added or changed? Have any new applications
 been deployed? If changes have been made recently, consider backing them
 out and seeing what happens — does the problem still occur?
 * Was the feature or functionality working correctly at one time? If so,
 what changed or happened between then and now?
 * Is this working on another system? If so, what is different about that
 environment?

 [[abgax]][[GSTSG00173]][[examining-log-files]]

 ==== Examining Log Files

 Logging is one of your most important troubleshooting tools. It is the
 process by which {productName} captures data
 about events that occur during server operation, such as configuration
 errors, security failures, or server malfunction. This data is recorded
 in log files, and is usually your first source of information when
 Enterprise Server problems occur. The primary purpose of log files is to
 provide troubleshooting information. Analyzing the log files can help
 determine the health of the server and identify problem areas.

 By default, log information for each {productName} server instance is captured in a `server.log` file. That is,
 each instance, including the domain administration server (DAS), has an
 individual log file. By default, the log file for the DAS is located in
 domain-dir``/logs``, and the log file for each instance is located in
 instance-dir``/logs`.

 In addition, for domains that use clustering, {productName} captures log information for each cluster instance in a
 `cluster.log` file. By default, the `cluster.log` file is also located
 in instance-dir``/logs``.

 Oracle recommends using the Administration Console to view logging
 information. However, you can open a log file in a text editor and
 search for the module or message in which you are interested. {productName} also lets you collect log files into a ZIP
 file, which provides a convenient means to collect and view the log
 files for an instance or a domain even when it is not running.

 You configure the Logging Service by setting attributes in the
 `logging.properties` file. Each server, configuration, instance, and
 cluster in the {productName} domain has an
 individual `logging.properties` file. The root directory in which these
 `logging.properties` files are located is the same directory as for the
 `domain.xml` file, typically domain-dir/`config`. The default target
 when configuring logging attributes is the DAS. However, you can
 optionally target a specific server, instance, or cluster. You can also
 target a configuration that is shared by one or more instances or
 clusters. The Logging Service can also be configured using the
 Administration Console.

 Log levels such as `SEVERE`, `WARNING`, `INFO`, `CONFIG`, and others can
 be set to provide different types and amounts of information. The
 default setting is `INFO`. Each {productName}
 module has its own logger, and each logger has its own namespace. Log
 levels can be set globally for all loggers, or individually for
 module-specific loggers.

 For information about using the Administration Console log viewer and
 logging functions, see the Administration Console online help. For
 information about using the command line for logging functions, see
 "link:administration-guide/logging.html#GSADG00010[Administering the Logging Service]" in {productName} Administration Guide.

 [[ghuvd]][[GSTSG00174]][[monitoring-the-system]]

 ==== Monitoring the System

 Monitoring is another helpful tool. It is the process of reviewing the
 statistics of a system to improve performance or solve problems. By
 monitoring the state of various components and services deployed in
 {productName} you can identify performance
 bottlenecks, predict failures, perform root cause analysis, and ensure
 that everything is functioning as expected. For more information about
 monitoring, including JConsole information, see
 "link:administration-guide/monitoring.html#GSADG00011[Administering the Monitoring Service]" in {productName} Administration Guide.

 [[ghuvy]][[GSTSG00040]][[troubleshooting-tools]]

 === Troubleshooting Tools

 Several tools are available that can be used to collect information for
 troubleshooting purposes. This section provides basic information about
 some of them, and includes the following:

 * link:#ghvcm[Operating System Utilities]
 * link:#ghvbo[Stack Traces and Thread Dumps]
 * link:#ghyjq[VisualVM]
 * link:#gjjjl[JVM Command-Line Tools]

 [[ghvcm]][[GSTSG00175]][[operating-system-utilities]]

 ==== Operating System Utilities

 Operating system utilities, such as `pkginfo` and `showrev` on Solaris
 and `rpm` on Linux, are helpful in gathering system information.

 The `ps -ef` command provides helpful information about processes that
 are running, including their process identification numbers (PIDs).

 [[ghvbo]][[GSTSG00176]][[stack-traces-and-thread-dumps]]

 ==== Stack Traces and Thread Dumps

 A stack trace is a user-friendly snapshot of the threads and monitors in
 a Virtual Machine for the Java platform (Java Virtual Machine or JVM
 machine). A thread dump shows what every thread in a JVM is doing at a
 given time and is useful in debugging. When the application server
 freezes, hangs, or becomes sluggish for no apparent reason, you should
 generate and analyze a thread dump.

 This section explains how to obtain a thread dump for {productName}. More information about analyzing the information
 contained in a thread dump can be found in
 "http://java.sun.com/developer/technicalArticles/Programming/Stacktrace[An
 Introduction to Java Stack Traces]"
 (`http://java.sun.com/developer/technicalArticles/Programming/Stacktrace`).

 [[ghykr]][[GSTSG00023]][[to-obtain-a-server-thread-dump]]

 ===== To Obtain a Server Thread Dump

 Type the following command:

 [source]
 ----
 asadmin generate-jvm-report --type=thread
 ----

 [[sthref3]]

 See Also

 link:reference-manual/generate-jvm-report.html#GSRFM00138[`generate-jvm-report`(1)]

 [[ghyjq]][[GSTSG00177]][[visualvm]]

 ==== VisualVM

 VisualVM is a Java troubleshooting tool that uses various technologies
 such as `jvmstat`, JMX, and Attach API to access monitored applications.
 VisualVM is a tool for visualizing data sources and by default
 visualizes the following types: applications, hosts, snapshots, core
 dumps, heap dumps, and thread dumps. These data sources are visualized
 in VisualVM so that they can be monitored for the purposes of analysis,
 management, and troubleshooting. VisualVM is commonly used to detect
 memory leaks.

 VisualVM has a GlassFish plugin that enhances monitoring of hosted
 applications by adding specialized overview, a tab for monitoring the
 HTTP Service, and the ability to visually select and monitor any of the
 deployed web applications. You can experiment with VisualVM
 troubleshooting capabilities, but note that various features depend on
 the Java versions used in the client and server. Depending on your
 configuration, you might only get parts of the VisualVM features. For
 more information about VisualVM, see `http://visualvm.java.net`.

 [[gjjjl]][[GSTSG00178]][[jvm-command-line-tools]]

 ==== JVM Command-Line Tools

 JVM command-line tools can be used to provide valuable information about
 hung Java processes or Java core dumps. These tools include the
 following:

 * `jstack`: Prints Java stack traces of Java threads for a given Java
 process or core file or a remote debug server.
 * `jinfo`: Prints Java configuration information for a given Java
 process or core file or a remote debug server.
 * `jmap`: Prints shared object memory maps or heap memory details for a
 given process or core file or a remote debug server.
 * `jsadebugd`: Attaches to a Java process or core file and acts as a
 debug server. Remote clients such as `jstack`, `jmap`, and `jinfo` can
 attach to the server using Java Remote Invocation Method (RMI).
 * `jhat`: Enables Java heap dumps to be browsed using a web browser.
 * `jstat`: Displays performance statistics for an instrumented HotSpot JVM.
 * `jps`: Lists the instrumented HotSpot JVMs on the target system

 [[ghuyv]][[GSTSG00041]][[where-to-go-for-more-information]]

 === Where to Go for More Information

 These resources were mentioned throughout this chapter and are provided
 again here for easy reference.

 * Release Notes: link:release-notes.html#GSRLN[{productName}
 Release Notes]
 * Error messages: link:error-messages-reference.html#GSEMR[{productName} Error
 Message Reference]
 * Mailing lists and forums: See link:#ghymp[Search the GlassFish Mailing
 Lists and Forums] for details about accessing lists and forums.
 * GlassFish community site: `http://glassfish.java.net/`
	type=page
	status=published
	title=Overview of {productName} Troubleshooting
	next=specific-issues.html
	prev=preface.html
	~~~~~~

	= Overview of {productName} Troubleshooting

	[[GSTSG00002]][[abgap]]


	[[overview-of-glassfish-server-open-source-edition-troubleshooting]]
	== 1 Overview of {productName} Troubleshooting

	This chapter describes some of the tools, methods, and resources
	available for troubleshooting {productName}.
	Guidelines for evaluating and investigating a problem are provided.

	This chapter contains the following sections:

	* link:#abgar[Identifying the Problem]
	* link:#ghuvy[Troubleshooting Tools]
	* link:#ghuyv[Where to Go for More Information]

	[[abgar]][[GSTSG00039]][[identifying-the-problem]]

	=== Identifying the Problem

	Application servers are typically deployed in complex operating
	environments and involve many technologies, products, and tools.
	Understanding and diagnosing problems in enterprise software with many
	components performing many tasks can be a challenge. This section
	describes how to get started , and contains the following topics:

	* link:#ghvay[First Steps]
	* link:#ghuvf[Gathering Information]
	* link:#abgax[Examining Log Files]
	* link:#ghuvd[Monitoring the System]

	[[ghvay]][[GSTSG00171]][[first-steps]]

	==== First Steps

	Sometimes the most obvious solutions are overlooked. As you begin your
	investigation, try the following steps first.

	[[ghyku]][[GSTSG00077]][[verify-system-requirements-and-configuration]]

	===== Verify System Requirements and Configuration

	Ensure that your system meets the requirements listed in
	"link:release-notes/release-notes.html#GSRLN00131[Hardware and Software Requirements]"
	in {productName} Release Notes.
	Problems are likely to arise if you attempt to install on a platform that
	is not supported or on a system that in some other way does not meet release requirements.
	Also see "link:release-notes/release-notes.html#GSRLN00253[Known Issues]"
	in {productName} Release Notes for known issues related to installation.

	{productName} requires JDK release 6. The minimum
	(and certified) version of the JDK that is required for {productName} depends on the operating system:

	* For supported operating systems except Mac OS, the minimum required version is 1.6.0_17.
	* For the Mac OS X operating system, the minimum required version is 1.6.0_15.

	If necessary, download and install the required JDK software.

	On Solaris, Linux, and Windows systems, JDK software is available from the
	http://www.oracle.com/technetwork/java/javase/downloads/index.html[
	Java SE downloads page]
	(`http://www.oracle.com/technetwork/java/javase/downloads/index.html`).

	For Mac OS X systems, {productName} uses the JDK
	that is part of the Macintosh operating system. If necessary, obtain the
	required JDK version from the http://support.apple.com/downloads/[Mac OS
	X Updates site] (`http://support.apple.com/downloads/`).

	Also ensure that the `JAVA_HOME` environment variable on your system
	points to the JDK installation directory and not the Java Runtime
	Environment (JRE) software.

	Set `JAVA_HOME` and `$JAVA_HOME/bin` in the `PATH` to point to the
	supported JDK version.

	[[ghyml]][[GSTSG00078]][[review-known-issues]]

	===== Review Known Issues

	Your problem might be related to a known issue for the release. Refer to
	the link:release-notes.html#GSRLN[{productName} Release Notes] for
	the latest information regarding known issues and possible workarounds.
	Also search the GlassFish Issue Tracker at
	`http://java.net/jira/browse/GLASSFISH`.

	[[ghykl]][[GSTSG00079]][[search-the-product-documentation]]

	===== Search the Product Documentation

	{productName} includes complete product
	documentation. Search the documentation to see if your problem is
	addressed. See link:preface.html#ghpbz[{productName} Documentation
	Set] for the books in the documentation set and a description of their
	contents. Also see the Administration Console online help for detailed
	information about performing administrative tasks using the graphical
	interface.

	The following books will be especially helpful for troubleshooting:

	* link:release-notes.html#GSRLN[{productName} Release Notes],
	which provides the latest information regarding known issues and possible workarounds.
	* link:error-messages-reference.html#GSEMR[
	{productName} Error Message Reference],
	which lists error messages you might encounter when using {productName}.

	Use the product documentation to learn more about {productName}. The more you know about the product the easier it might
	be to figure out why something isn't working.

	[[ghymp]][[GSTSG00080]][[search-the-glassfish-mailing-lists-and-forums]]

	===== Search the GlassFish Mailing Lists and Forums

	Lists and forums are extremely helpful resources, and are accessed as follows:

	* GlassFish mailing lists (start with users@glassfish.java.net and
	search the archives): `http://java.net/projects/glassfish/lists/`
	* GlassFish user forum: `http://www.java.net/forums/glassfish/glassfish`

	[[ghuvf]][[GSTSG00172]][[gathering-information]]

	==== Gathering Information

	Troubleshooting and analysis require information. The more information
	you have the easier it is to classify a problem and search for its
	solution. Detailed information will also be necessary should you need to
	contact others for support, either through a community mailing list or
	through more formal Sun support channels.

	As you continue your investigation, consider the following questions.

	[[ghvar]][[GSTSG00081]][[when-does-the-problem-occur]]

	===== When Does the Problem Occur?

	* What do the logs show? What kind of error message are you getting? For
	more information about logs, see link:#abgax[Examining Log Files]. Logs
	are a good place to start your troubleshooting.
	* What are you trying to do when the problem occurs and how are you
	doing it? What is the sequence of events?
	* Does the problem occur every time you perform the same type of
	operation, or does it seem random? Can you reproduce the issue?
	* Have other events or problems occurred that could possibly be related,
	such as web sessions closing early, exceptions being thrown in your own
	application logic, components not being correctly deployed or
	undeployed?

	[[ghvbb]][[GSTSG00082]][[what-is-your-environment]]

	===== What Is Your Environment?

	* What version of {productName} are you using?
	What operating system and version? What JDK version? Many problems are
	caused simply because system requirements for the release are not met.
	Refer to the link:release-notes.html#GSRLN[{productName} Release
	Notes] for the latest information regarding system requirements, and
	make sure your system meets those requirements.
	* What resources does your system have, such as memory, disk, and swap
	space? If system memory is an issue, look for ways to optimize your
	configuration and consider taking other actions such as adding memory or
	decreasing system load.
	* Have any patches been applied? If so, what are the product and
	operating system patch numbers?
	* What other products and technologies are installed and being used in
	the installation?
	* How many application servers, web servers, and directory servers are
	installed? What are the products and versions?
	* How is the web server connected to {productName}? On the same system?
	* How is {productName} connected to the directory
	server?
	* What JDBC driver is being used to access the database?

	[[ghvce]][[GSTSG00083]][[what-is-your-system-configuration]]

	===== What Is Your System Configuration?

	* What are your settings?
	* On which port is {productName} configured — the
	default or something else?
	* What defaults were changed during installation and what are the
	values?
	* What other settings were changed from the defaults and what are their
	values?
	* What are the parameters related to JVM heap, stack, and garbage
	collection set to?
	* What are the JVM options?
	* What is the permgen size? `OutOfMemoryError:PermGen space` errors are
	common and indicate that you need to increase the permanent generation
	space available.
	* Is SSL enabled?
	* What are your network settings (proxy, firewall, and so on)? What
	happens if you disable your firewall and attempt the task?

	[[ghvcr]][[GSTSG00084]][[what-is-different]]

	===== What Is Different?

	* What is different that could have provoked the problem or triggered
	the event? Was something new added or changed? Have any new applications
	been deployed? If changes have been made recently, consider backing them
	out and seeing what happens — does the problem still occur?
	* Was the feature or functionality working correctly at one time? If so,
	what changed or happened between then and now?
	* Is this working on another system? If so, what is different about that
	environment?

	[[abgax]][[GSTSG00173]][[examining-log-files]]

	==== Examining Log Files

	Logging is one of your most important troubleshooting tools. It is the
	process by which {productName} captures data
	about events that occur during server operation, such as configuration
	errors, security failures, or server malfunction. This data is recorded
	in log files, and is usually your first source of information when
	Enterprise Server problems occur. The primary purpose of log files is to
	provide troubleshooting information. Analyzing the log files can help
	determine the health of the server and identify problem areas.

	By default, log information for each {productName} server instance is captured in a `server.log` file. That is,
	each instance, including the domain administration server (DAS), has an
	individual log file. By default, the log file for the DAS is located in
	domain-dir``/logs``, and the log file for each instance is located in
	instance-dir``/logs`.

	In addition, for domains that use clustering, {productName} captures log information for each cluster instance in a
	`cluster.log` file. By default, the `cluster.log` file is also located
	in instance-dir``/logs``.

	Oracle recommends using the Administration Console to view logging
	information. However, you can open a log file in a text editor and
	search for the module or message in which you are interested. {productName} also lets you collect log files into a ZIP
	file, which provides a convenient means to collect and view the log
	files for an instance or a domain even when it is not running.

	You configure the Logging Service by setting attributes in the
	`logging.properties` file. Each server, configuration, instance, and
	cluster in the {productName} domain has an
	individual `logging.properties` file. The root directory in which these
	`logging.properties` files are located is the same directory as for the
	`domain.xml` file, typically domain-dir/`config`. The default target
	when configuring logging attributes is the DAS. However, you can
	optionally target a specific server, instance, or cluster. You can also
	target a configuration that is shared by one or more instances or
	clusters. The Logging Service can also be configured using the
	Administration Console.

	Log levels such as `SEVERE`, `WARNING`, `INFO`, `CONFIG`, and others can
	be set to provide different types and amounts of information. The
	default setting is `INFO`. Each {productName}
	module has its own logger, and each logger has its own namespace. Log
	levels can be set globally for all loggers, or individually for
	module-specific loggers.

	For information about using the Administration Console log viewer and
	logging functions, see the Administration Console online help. For
	information about using the command line for logging functions, see
	"link:administration-guide/logging.html#GSADG00010[Administering the Logging Service]" in {productName} Administration Guide.

	[[ghuvd]][[GSTSG00174]][[monitoring-the-system]]

	==== Monitoring the System

	Monitoring is another helpful tool. It is the process of reviewing the
	statistics of a system to improve performance or solve problems. By
	monitoring the state of various components and services deployed in
	{productName} you can identify performance
	bottlenecks, predict failures, perform root cause analysis, and ensure
	that everything is functioning as expected. For more information about
	monitoring, including JConsole information, see
	"link:administration-guide/monitoring.html#GSADG00011[Administering the Monitoring Service]" in {productName} Administration Guide.

	[[ghuvy]][[GSTSG00040]][[troubleshooting-tools]]

	=== Troubleshooting Tools

	Several tools are available that can be used to collect information for
	troubleshooting purposes. This section provides basic information about
	some of them, and includes the following:

	* link:#ghvcm[Operating System Utilities]
	* link:#ghvbo[Stack Traces and Thread Dumps]
	* link:#ghyjq[VisualVM]
	* link:#gjjjl[JVM Command-Line Tools]

	[[ghvcm]][[GSTSG00175]][[operating-system-utilities]]

	==== Operating System Utilities

	Operating system utilities, such as `pkginfo` and `showrev` on Solaris
	and `rpm` on Linux, are helpful in gathering system information.

	The `ps -ef` command provides helpful information about processes that
	are running, including their process identification numbers (PIDs).

	[[ghvbo]][[GSTSG00176]][[stack-traces-and-thread-dumps]]

	==== Stack Traces and Thread Dumps

	A stack trace is a user-friendly snapshot of the threads and monitors in
	a Virtual Machine for the Java platform (Java Virtual Machine or JVM
	machine). A thread dump shows what every thread in a JVM is doing at a
	given time and is useful in debugging. When the application server
	freezes, hangs, or becomes sluggish for no apparent reason, you should
	generate and analyze a thread dump.

	This section explains how to obtain a thread dump for {productName}. More information about analyzing the information
	contained in a thread dump can be found in
	"http://java.sun.com/developer/technicalArticles/Programming/Stacktrace[An
	Introduction to Java Stack Traces]"
	(`http://java.sun.com/developer/technicalArticles/Programming/Stacktrace`).

	[[ghykr]][[GSTSG00023]][[to-obtain-a-server-thread-dump]]

	===== To Obtain a Server Thread Dump

	Type the following command:

	[source]
	----
	asadmin generate-jvm-report --type=thread
	----

	[[sthref3]]

	See Also

	link:reference-manual/generate-jvm-report.html#GSRFM00138[`generate-jvm-report`(1)]

	[[ghyjq]][[GSTSG00177]][[visualvm]]

	==== VisualVM

	VisualVM is a Java troubleshooting tool that uses various technologies
	such as `jvmstat`, JMX, and Attach API to access monitored applications.
	VisualVM is a tool for visualizing data sources and by default
	visualizes the following types: applications, hosts, snapshots, core
	dumps, heap dumps, and thread dumps. These data sources are visualized
	in VisualVM so that they can be monitored for the purposes of analysis,
	management, and troubleshooting. VisualVM is commonly used to detect
	memory leaks.

	VisualVM has a GlassFish plugin that enhances monitoring of hosted
	applications by adding specialized overview, a tab for monitoring the
	HTTP Service, and the ability to visually select and monitor any of the
	deployed web applications. You can experiment with VisualVM
	troubleshooting capabilities, but note that various features depend on
	the Java versions used in the client and server. Depending on your
	configuration, you might only get parts of the VisualVM features. For
	more information about VisualVM, see `http://visualvm.java.net`.

	[[gjjjl]][[GSTSG00178]][[jvm-command-line-tools]]

	==== JVM Command-Line Tools

	JVM command-line tools can be used to provide valuable information about
	hung Java processes or Java core dumps. These tools include the
	following:

	* `jstack`: Prints Java stack traces of Java threads for a given Java
	process or core file or a remote debug server.
	* `jinfo`: Prints Java configuration information for a given Java
	process or core file or a remote debug server.
	* `jmap`: Prints shared object memory maps or heap memory details for a
	given process or core file or a remote debug server.
	* `jsadebugd`: Attaches to a Java process or core file and acts as a
	debug server. Remote clients such as `jstack`, `jmap`, and `jinfo` can
	attach to the server using Java Remote Invocation Method (RMI).
	* `jhat`: Enables Java heap dumps to be browsed using a web browser.
	* `jstat`: Displays performance statistics for an instrumented HotSpot JVM.
	* `jps`: Lists the instrumented HotSpot JVMs on the target system

	[[ghuyv]][[GSTSG00041]][[where-to-go-for-more-information]]

	=== Where to Go for More Information

	These resources were mentioned throughout this chapter and are provided
	again here for easy reference.

	* Release Notes: link:release-notes.html#GSRLN[{productName}
	Release Notes]
	* Error messages: link:error-messages-reference.html#GSEMR[{productName} Error
	Message Reference]
	* Mailing lists and forums: See link:#ghymp[Search the GlassFish Mailing
	Lists and Forums] for details about accessing lists and forums.
	* GlassFish community site: `http://glassfish.java.net/`