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 	<h1 class="title topictitle1">Basic Tutorial</h1>


 	<div class="body taskbody">
 		<div class="section context">
 			<p class="p">
 				This tutorial provides a "jumping-off place" to get familiar with
 				Memory Analyzer.
 			</p>


 			<p class="p">
 				If you are using Memory Analyzer installed into Eclipse rather than a stand-alone Memory Analyzer,
 				first open the 'Memory Analysis' perspective using:
 				<span class="ph menucascade"><span class="ph uicontrol">Window</span> &gt; <span class="ph uicontrol">Perspective</span> &gt; <span class="ph uicontrol">Open Perspective</span> &gt; <span class="ph uicontrol">Other ...</span> &gt; <span class="ph uicontrol">Memory Analysis</span></span>
 			</p>


 			<p class="p">
 				<strong class="ph b">Step 1 - Getting a Heap Dump</strong>
 			</p>


 			<p class="p">
 				The Memory Analyzer works with
 				<a class="xref" href="../concepts/heapdump.html">heap dumps</a>
 				. Such a heap dump contains information about all Java objects alive
 				at a given point in time. All current Java Virtual Machines can
 				write heap dumps, but the exact steps depend on vendor, version and
 				operation system. Find out more in the section
 				<a class="xref" href="../tasks/acquiringheapdump.html">Acquiring Heap Dumps</a>
 				.
 			</p>


 			<p class="p">
 				Open
 				<img class="image" src="../mimes/me76fc4.png" alt=""/>
 				<a class="xref" href="javascript:liveAction(%22org.eclipse.mat.ui%22,%22org.eclipse.mat.ui.snapshot.actions.OpenSampleHeapDumpAction%22,%22org.eclipse.mat.ui.help/heapdump/HeapDumpSample.hprof%22)">
 					a sample heap dump</a>
 				if you view this page inside the Eclipse help center.
 			</p>


 			<p class="p">
 				For the purpose of this tutorial, we use Java 6 and JConsole on
 				Windows. Start your application with Java 6, then start
 				<samp class="ph codeph">&lt;jre6&gt;/bin/jconsole.exe</samp>
 				and select the running application (in this case Eclipse):
 			</p>


 			<img class="image" src="basictutorial_jconsole_open.png" alt="JConsole dialog to open a connection to a Virtual Machine."/>

 			<p class="p">
 				Then, select the operation
 				<em class="ph i">dumpHeap</em>
 				from the
 				<em class="ph i">com.sun.management.HotSpotDiagnostic</em>
 				MBean. The first parameter
 				<em class="ph i">p0</em>
 				is the full path to the heap dump file. Make sure you give it the
 				file extension .hprof. The second parameter
 				<em class="ph i">p1</em>
 				should be left at true as we are only interested in live objects.
 			</p>


 			<img class="image" src="basictutorial_jconsole_mbean.png" alt="Select the dumpHeap method of the HotspotDiagnostics mbean."/>

 			<p class="p">
 				<strong class="ph b">Step 2 - The Overview</strong>
 			</p>


 			<p class="p">
 				Open the heap dump via
 				<span class="ph menucascade"><span class="ph uicontrol">File</span> &gt; <span class="ph uicontrol">
 						<img class="image" src="../mimes/i-openhd.png" alt=""/>
 						Open Heap Dump...
 					</span></span>
 				to see the overview page.
 			</p>


 			<img class="image" src="basictutorial_overview.png" alt="Memory Analyzer's overview page for a heap dump"/>

 			<p class="p">
 				On the right, you'll find the size of the dump and the number of
 				classes, objects and class loaders.
 			</p>

 			<p class="p">
 				If the total size of the dump is much smaller than the size of the file it is possible
 				that the heap dump contained many 'garbage' objects which would be discarded at the next garbage
 				collection. See the <a class="xref" href="../reference/inspections/unreachable_objects.html" title="Find out more about objects that could or should be garbage collected.">unreachable objects</a>
 				query to examine these 'garbage' objects.
 			</p>

 			<p class="p">
 				Right below, the pie chart gives an impression on the biggest
 				objects in the dump. Move your mouse over a slice to see the details
 				of the objects in the object inspector on the left. Click on any
 				slice to drill down and follow for example the outgoing references.
 			</p>


 			<p class="p">
 				<strong class="ph b">Step 3 - The Histogram</strong>
 			</p>


 			<p class="p">
 				Select the
 				<em class="ph i">histogram</em>
 				from the tool bar to list the number of instances per class, the
 				<a class="xref" href="../concepts/shallowretainedheap.html">shallow size</a>
 				and the
 				<a class="xref" href="../concepts/shallowretainedheap.html">retained size</a>
 				.
 			</p>


 			<img class="image" src="basictutorial_histogram.png" alt="Histogram"/>

 			<p class="p">
 				The Memory Analyzer displays by default the retained size of
 				individual objects. However, the retained size of a set of objects -
 				in this case all instances of a particular class - needs to be
 				calculated.
 			</p>


 			<p class="p">
 				To approximate the retained sizes for all rows, pick
 				<img class="image" src="../mimes/i-calcrs.png" alt="Calculate retained size"/> icon
 				from the tool bar. Alternatively, select a couple rows and use the
 				context menu.
 			</p>


 			<img class="image" src="basictutorial_calc_retained.png" alt="Select calculate retained sizes from the tool bar"/>

 			<p class="p">
 				Using the
 				<strong class="ph b">context menu</strong>
 				, you can drill-down into the set of objects
 				which the selected row
 				represents. For example, you can list the
 				objects with outgoing or
 				incoming references. Or group the objects
 				by the value of an
 				attribute. Or group the collections by their
 				size. Or or or...
 			</p>


 			<p class="p">
 				One thing that makes the Memory Analyzer so powerful is the fact
 				that one can run any action on any set of objects. Just drill down
 				and slice your objects the way you need them.
 			</p>


 			<img class="image" src="basictutorial_context_menu.png" alt="Drill down via the context menu"/>

 			<p class="p">
 				Another important feature is the facility to
 				<strong class="ph b">group any histogram by class loader, packages or superclass</strong>
 				.
 			</p>


 			<img class="image" src="basictutorial_group_by.png" alt="Group the histogram by class loader or package via the tool bar"/>

 			<p class="p">
 				Any decent application loads different components by different
 				class loaders. The Memory Analyzer attaches a meaningful label to
 				the class loader - in the case of OSGi bundles it is the bundle id.
 				Therefore it becomes a lot easier to divide the heap dump into
 				smaller parts.
 			</p>


 			<p class="p">
 				More: <a class="xref" href="../tasks/analyzingclassloader.html" title="Class loaders load classes into the memory of the JVM. When analyzing the heap, class loaders are very important for two reasons: First, applications typically load components using separate class loaders. Second, the loaded classes are usually stored in a separate space (e.g. the perm space) which can also be depleted.">Analyze Class Loader</a>
 			</p>


 			<img class="image" src="basictutorail_by_classloader.png" alt="Histogram grouped by class loader"/>

 			<p class="p">
 				Grouping the histogram by packages allows to drill-down along the
 				Java package hierarchy.
 			</p>


 			<img class="image" src="basictutorail_by_package.png" alt="Histogram grouped by packages"/>

 			<p class="p">
 				Grouping the histogram by superclass provides an easy way to find for example all the subclasses of java.util.AbstractMap, etc...
 			</p>


 			<img class="image" src="basictutorial_by_superclass.png" alt="Histogram grouped by superclass"/>

 			<p class="p">
 				<strong class="ph b">Step 4 - The Dominator Tree</strong>
 			</p>


 			<p class="p">
 				The
 				<a class="xref" href="../concepts/dominatortree.html">dominator tree</a>
 				displays the biggest objects in the heap dump. The next level of the
 				tree lists those objects that would be garbage collected if all
 				incoming references to the parent node were removed.
 			</p>


 			<p class="p">
 				The dominator tree is a powerful tool to investigate which objects
 				keep which other objects alive. Again, the tree can be grouped by
 				class loader (e.g. components) and packages to ease the analysis.
 			</p>


 			<img class="image" src="basictutorial_dominator_tree.png" alt="Dominator Tree"/>

 			<p class="p">
 				<strong class="ph b">Step 5 - Path to GC Roots</strong>
 			</p>


 			<p class="p">
 				<a class="xref" href="../concepts/gcroots.html">Garbage Collections Roots (GC roots)</a>
 				are objects that are kept alive by the Virtual Machines itself.
 				These include for example the thread objects of the threads
 				currently running, objects currently on the call stack and classes
 				loaded by the system class loader.
 			</p>


 			<p class="p">
 				The (reverse) reference chain from an object to a GC root - the so
 				called path to GC roots - explains why the object cannot be garbage
 				collected. The path helps solving the classical memory leak in Java:
 				those leaks exist because an object is still referenced even though
 				the program logic will not access the object anymore.
 			</p>


 			<img class="image" src="basictutorial_path_menu.png" alt="Select path to GC roots from the context menu"/>

 			<p class="p">
 				Initially, the GC root reached by the shortest path is selected.
 			</p>


 			<img class="image" src="basictutorial_path.png" alt="Path to GC roots"/>

 			<p class="p">
 				<strong class="ph b">Step 6 - The Leak Report</strong>
 			</p>


 			<p class="p">
 				The Memory Analyzer can inspect the heap dump for leak suspects,
 				e.g. objects or set of objects which are suspiciously big.
 			</p>


 			<img class="image" src="basictutorial_run_leak_suspects.png" alt="Run the leak report"/>

 			<p class="p">
 				Learn more in this blog posting:
 				<a class="xref" href="http://memoryanalyzer.blogspot.com/2008/05/automated-heap-dump-analysis-finding.html">Automated Heap Dump Analysis: Finding Memory Leaks with One
 					Click</a>
 				.
 			</p>

 		</div>

 	</div>

 	<div class="related-links"><div class="relinfo relconcepts"><strong>Related concepts</strong><br/>
 <div><a class="link" href="../concepts/dominatortree.html">Dominator Tree</a></div>
 <div><a class="link" href="../concepts/gcroots.html">Garbage Collection Roots</a></div>
 </div>
 </div>

 </body>
 </html>
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	PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
	<html xml:lang="en-us" lang="en-us">
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	<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
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	<meta name="DC.Title" content="Basic Tutorial"/>
	<meta name="DC.Relation" scheme="URI" content="../concepts/dominatortree.html"/>
	<meta name="DC.Relation" scheme="URI" content="../concepts/gcroots.html"/>
	<meta name="copyright" content="Copyright (c) 2008, 2017 SAP AG and others. All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License v1.0 which accompanies this distribution, and is available at http://www.eclipse.org/legal/epl-v10.html " type="primary"/>
	<meta name="DC.Rights.Owner" content="Copyright (c) 2008, 2017 SAP AG and others. All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License v1.0 which accompanies this distribution, and is available at http://www.eclipse.org/legal/epl-v10.html " type="primary"/>
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	<title>Basic Tutorial</title>
	</head>
	<body id="task_basictutorial">


	<h1 class="title topictitle1">Basic Tutorial</h1>



	<div class="body taskbody">
	<div class="section context">
	<p class="p">
	This tutorial provides a "jumping-off place" to get familiar with
	Memory Analyzer.
	</p>


	<p class="p">
	If you are using Memory Analyzer installed into Eclipse rather than a stand-alone Memory Analyzer,
	first open the 'Memory Analysis' perspective using:
	<span class="ph menucascade"><span class="ph uicontrol">Window</span> > <span class="ph uicontrol">Perspective</span> > <span class="ph uicontrol">Open Perspective</span> > <span class="ph uicontrol">Other ...</span> > <span class="ph uicontrol">Memory Analysis</span></span>
	</p>


	<p class="p">
	<strong class="ph b">Step 1 - Getting a Heap Dump</strong>
	</p>


	<p class="p">
	The Memory Analyzer works with
	<a class="xref" href="../concepts/heapdump.html">heap dumps</a>
	. Such a heap dump contains information about all Java objects alive
	at a given point in time. All current Java Virtual Machines can
	write heap dumps, but the exact steps depend on vendor, version and
	operation system. Find out more in the section
	<a class="xref" href="../tasks/acquiringheapdump.html">Acquiring Heap Dumps</a>
	.
	</p>


	<p class="p">
	Open
	<img class="image" src="../mimes/me76fc4.png" alt=""/>
	<a class="xref" href="javascript:liveAction(%22org.eclipse.mat.ui%22,%22org.eclipse.mat.ui.snapshot.actions.OpenSampleHeapDumpAction%22,%22org.eclipse.mat.ui.help/heapdump/HeapDumpSample.hprof%22)">
	a sample heap dump</a>
	if you view this page inside the Eclipse help center.
	</p>


	<p class="p">
	For the purpose of this tutorial, we use Java 6 and JConsole on
	Windows. Start your application with Java 6, then start
	<samp class="ph codeph"><jre6>/bin/jconsole.exe</samp>
	and select the running application (in this case Eclipse):
	</p>


	<img class="image" src="basictutorial_jconsole_open.png" alt="JConsole dialog to open a connection to a Virtual Machine."/>

	<p class="p">
	Then, select the operation
	<em class="ph i">dumpHeap</em>
	from the
	<em class="ph i">com.sun.management.HotSpotDiagnostic</em>
	MBean. The first parameter
	<em class="ph i">p0</em>
	is the full path to the heap dump file. Make sure you give it the
	file extension .hprof. The second parameter
	<em class="ph i">p1</em>
	should be left at true as we are only interested in live objects.
	</p>


	<img class="image" src="basictutorial_jconsole_mbean.png" alt="Select the dumpHeap method of the HotspotDiagnostics mbean."/>

	<p class="p">
	<strong class="ph b">Step 2 - The Overview</strong>
	</p>


	<p class="p">
	Open the heap dump via
	<span class="ph menucascade"><span class="ph uicontrol">File</span> > <span class="ph uicontrol">
	<img class="image" src="../mimes/i-openhd.png" alt=""/>
	Open Heap Dump...
	</span></span>
	to see the overview page.
	</p>


	<img class="image" src="basictutorial_overview.png" alt="Memory Analyzer's overview page for a heap dump"/>

	<p class="p">
	On the right, you'll find the size of the dump and the number of
	classes, objects and class loaders.
	</p>

	<p class="p">
	If the total size of the dump is much smaller than the size of the file it is possible
	that the heap dump contained many 'garbage' objects which would be discarded at the next garbage
	collection. See the <a class="xref" href="../reference/inspections/unreachable_objects.html" title="Find out more about objects that could or should be garbage collected.">unreachable objects</a>
	query to examine these 'garbage' objects.
	</p>

	<p class="p">
	Right below, the pie chart gives an impression on the biggest
	objects in the dump. Move your mouse over a slice to see the details
	of the objects in the object inspector on the left. Click on any
	slice to drill down and follow for example the outgoing references.
	</p>


	<p class="p">
	<strong class="ph b">Step 3 - The Histogram</strong>
	</p>


	<p class="p">
	Select the
	<em class="ph i">histogram</em>
	from the tool bar to list the number of instances per class, the
	<a class="xref" href="../concepts/shallowretainedheap.html">shallow size</a>
	and the
	<a class="xref" href="../concepts/shallowretainedheap.html">retained size</a>
	.
	</p>


	<img class="image" src="basictutorial_histogram.png" alt="Histogram"/>

	<p class="p">
	The Memory Analyzer displays by default the retained size of
	individual objects. However, the retained size of a set of objects -
	in this case all instances of a particular class - needs to be
	calculated.
	</p>


	<p class="p">
	To approximate the retained sizes for all rows, pick
	<img class="image" src="../mimes/i-calcrs.png" alt="Calculate retained size"/> icon
	from the tool bar. Alternatively, select a couple rows and use the
	context menu.
	</p>


	<img class="image" src="basictutorial_calc_retained.png" alt="Select calculate retained sizes from the tool bar"/>

	<p class="p">
	Using the
	<strong class="ph b">context menu</strong>
	, you can drill-down into the set of objects
	which the selected row
	represents. For example, you can list the
	objects with outgoing or
	incoming references. Or group the objects
	by the value of an
	attribute. Or group the collections by their
	size. Or or or...
	</p>


	<p class="p">
	One thing that makes the Memory Analyzer so powerful is the fact
	that one can run any action on any set of objects. Just drill down
	and slice your objects the way you need them.
	</p>


	<img class="image" src="basictutorial_context_menu.png" alt="Drill down via the context menu"/>

	<p class="p">
	Another important feature is the facility to
	<strong class="ph b">group any histogram by class loader, packages or superclass</strong>
	.
	</p>


	<img class="image" src="basictutorial_group_by.png" alt="Group the histogram by class loader or package via the tool bar"/>

	<p class="p">
	Any decent application loads different components by different
	class loaders. The Memory Analyzer attaches a meaningful label to
	the class loader - in the case of OSGi bundles it is the bundle id.
	Therefore it becomes a lot easier to divide the heap dump into
	smaller parts.
	</p>


	<p class="p">
	More: <a class="xref" href="../tasks/analyzingclassloader.html" title="Class loaders load classes into the memory of the JVM. When analyzing the heap, class loaders are very important for two reasons: First, applications typically load components using separate class loaders. Second, the loaded classes are usually stored in a separate space (e.g. the perm space) which can also be depleted.">Analyze Class Loader</a>
	</p>


	<img class="image" src="basictutorail_by_classloader.png" alt="Histogram grouped by class loader"/>

	<p class="p">
	Grouping the histogram by packages allows to drill-down along the
	Java package hierarchy.
	</p>


	<img class="image" src="basictutorail_by_package.png" alt="Histogram grouped by packages"/>

	<p class="p">
	Grouping the histogram by superclass provides an easy way to find for example all the subclasses of java.util.AbstractMap, etc...
	</p>


	<img class="image" src="basictutorial_by_superclass.png" alt="Histogram grouped by superclass"/>

	<p class="p">
	<strong class="ph b">Step 4 - The Dominator Tree</strong>
	</p>


	<p class="p">
	The
	<a class="xref" href="../concepts/dominatortree.html">dominator tree</a>
	displays the biggest objects in the heap dump. The next level of the
	tree lists those objects that would be garbage collected if all
	incoming references to the parent node were removed.
	</p>


	<p class="p">
	The dominator tree is a powerful tool to investigate which objects
	keep which other objects alive. Again, the tree can be grouped by
	class loader (e.g. components) and packages to ease the analysis.
	</p>


	<img class="image" src="basictutorial_dominator_tree.png" alt="Dominator Tree"/>

	<p class="p">
	<strong class="ph b">Step 5 - Path to GC Roots</strong>
	</p>


	<p class="p">
	<a class="xref" href="../concepts/gcroots.html">Garbage Collections Roots (GC roots)</a>
	are objects that are kept alive by the Virtual Machines itself.
	These include for example the thread objects of the threads
	currently running, objects currently on the call stack and classes
	loaded by the system class loader.
	</p>


	<p class="p">
	The (reverse) reference chain from an object to a GC root - the so
	called path to GC roots - explains why the object cannot be garbage
	collected. The path helps solving the classical memory leak in Java:
	those leaks exist because an object is still referenced even though
	the program logic will not access the object anymore.
	</p>


	<img class="image" src="basictutorial_path_menu.png" alt="Select path to GC roots from the context menu"/>

	<p class="p">
	Initially, the GC root reached by the shortest path is selected.
	</p>


	<img class="image" src="basictutorial_path.png" alt="Path to GC roots"/>

	<p class="p">
	<strong class="ph b">Step 6 - The Leak Report</strong>
	</p>


	<p class="p">
	The Memory Analyzer can inspect the heap dump for leak suspects,
	e.g. objects or set of objects which are suspiciously big.
	</p>


	<img class="image" src="basictutorial_run_leak_suspects.png" alt="Run the leak report"/>

	<p class="p">
	Learn more in this blog posting:
	<a class="xref" href="http://memoryanalyzer.blogspot.com/2008/05/automated-heap-dump-analysis-finding.html">Automated Heap Dump Analysis: Finding Memory Leaks with One
	Click</a>
	.
	</p>

	</div>

	</div>

	<div class="related-links"><div class="relinfo relconcepts"><strong>Related concepts</strong><br/>
	<div><a class="link" href="../concepts/dominatortree.html">Dominator Tree</a></div>
	<div><a class="link" href="../concepts/gcroots.html">Garbage Collection Roots</a></div>
	</div>
	</div>

	</body>
	</html>