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The JMX viewer provides access to data collected
from the operation of JMX servers inside the Java Virtual Machine
for Java 1.5.x versions. The viewer also provides you with the ability
to interject in some operations of the JVM and to manipulate the operation
and attributes of MBeans that you have defined. Using HPjmeter monitoring displays, you can observe the effect of changing the characteristics of MBeans that you
have loaded into the JMX server of the virtual machine. Opening the JMX viewer On opening a session with an application running
on Java 1.5.x, a data node displays in the main console to represent
current data collected from the JVM.
To access this summary data, double-click on the
summary JMX server node. The summary JMX Viewer opens. For information
on this part of the JMX Viewer, see Understanding the JMX Summary View. To manipulate some JVM and MBean functions on
this server, expand the summary node and double-click the entry labeled Modify JMX MBean data. The server JMX Viewer opens. For
information on this part of the JMX Viewer, see Changing Mbean Values and Monitoring the Result  |  |  |  |  | NOTE: This functionality is available only during an
open session. No record of the actions taken within the JMX viewer
are saved. To preserve a record of changes occurring in the application
run due to manipulation of the JMX server and MBeans, save the monitoring session
data for later review. Use the monitoring metric visualizers to view the saved
data. |  |  |  |  |
See also Understanding the JMX Summary View |  |
The JMX viewer opens in the Summary view with
five tabs displayed:
The Summary tab shows a collection of data about
the operating system and hardware, allocated memory, current heap
usage, and class loading status. Values are updated throughout the
duration of the open session.
Fluctuations in memory usage in heap and non-heap
areas are graphically displayed and periodically updated for the duration
of the open session. Mouse over the features of the graph to learn
what spaces are represented, as well as to learn what each of the
markers designates. The following image demonstrates some of the features
available on this tab.
Select
a region of interest Click the color bar in the graph to select the
memory space of interest. The bar will become outlined in blue and
the Region Details will update in the text area.
Consult the Region Details for updated information on memory usage in that region, total count
of garbage collections, and cumulative duration of GC events. Set
a usage threshold Where usage threshold can be set, a “0”
(zero) appears in the Usage Threshold box. To
set a threshold, replace the current value with a desired, valid value
in the box, and press Enter. To see what values are
valid for a region, mouse over the Usage Threshold box.
On pressing Enter, a red marker
will appear on the region usage bar to mark the point at which the
threshold is reached. The bar color turns red when the threshold is
reached and a notification is generated. Start
verbose GC At any point, you can click the verbose GC check
box to start collection of verbose GC data by the JVM. The JVM usually
writes this information to stdout. Uncheck the
box to stop logging verbose GC data.
Perform
a garbage collection At any point, you can click the Perform
GC button to force a System.gc garbage
collection on the heap.
HPjmeter locates and tracks the live threads processing
during the application run. This image shows available functions on
the Threads tab.
See
the list of live threads Pull the slider in the data pane to the right
to reveal the current list of live threads.
See
details for a selected thread Click a thread name in the left pane. Details
on thread activity and current state appear in the right pane.
Apply
a filter This filtering text box is useful when the thread
list is long. It allows you to reduce the list size according to the
starting letters of the thread name. To apply a filter, start typing
the first few distinguishing letters of the thread names that you
are interested in. The list will immediately be trimmed to entries
starting with those letters. Deleting text from the filter box returns
the list to its original state.
Detect
thread deadlock At any point, you can check the box for “Detect
Deadlock” to start monitoring specifically for thread deadlock
conditions. When a deadlock condition is encountered for a particular
thread, the text of the thread name turns red. Uncheck the box to
stop watching for this condition.
The Runtime tab summarizes
important characteristics of the runtime environment, including data
on the JVM version and uptime, options used to start the monitoring
agent, and some aspects of the hardware and operating system such
as memory assignment, swap space, and operating system type and version. Notifications triggered by changes that you make
using the JMX viewer appear on the Notifications tab. They are available for viewing for the duration of the open
session or until you clear them from the screen using the Clear All button. See also The MBean Notifications Tab Changing Mbean Values and Monitoring the Result |  |
Use the JMX server view to select the MBeans
that you want to look at in detail. The following image shows the
default view on opening the JMX server view. An explanation follows
the image.
JMX
MBean list filter Click this button to see a list of the filters that you can
apply to the MBean drop-down menu items at .
JMX
server drop-down menu The server from which this JMX viewer was launched
is shown in the “JMX Servers” drop-down menu.
JMX
MBean drop-down menu This drop-down menu lists the viewable MBeans
for which data can be displayed in the viewer. This list can get quite
long when viewing data for application servers. To reduce the list
length in the drop-down menu, click
the MBean filter button at .
JMX
MBean tab navigation Select an MBean, and the data for that bean is
displayed in the four tabs appearing immediately below the drop-down
menus. Click among the tabs to looks at various aspects of the selected
MBean. Four tabs are available in the JMX server view: Attributes, Operations, Notifications,
and Information.
JMX
MBean Details Viewer In the Detail Viewer, you
can drill down into the MBean data for details or to force an operation.
Using the Functions in the JMX Server View |  |
The following discussion touches on the basic
functions in this area of the JMX viewer. Click the MBean filter button to select a subset of MBeans to populate the
MBean drop-down menu. A small window opens that gives you the following
options for sorting the MBeans:
by domain (for example, java.lang, com.bea) by name (for example, ClassLoadingImpl, MBeanServerDelegate) by type (for example,GarbageCollector, MemoryPool)
Select the filter type that you want, and click
the Use Filter button. Use the MBean drop-down menu to see the resulting
list and to select an MBean to view. The Attribute tab lists the
contents of the selected MBean. In general, two actions are possible
at this level: drill down to see values of an attribute and change
the value of an attribute. The following image shows an example. An
explanation follows the image.
List
of name/value pairs found in the selected MBean The names are listed with their value. Values
may be dynamically updating; you may open them to reveal further details
as in , or you may edit them as in .
Clickable
value Names or values appearing in boldface type can
be opened to display details in the Detail Viewer area. Double-click the boldface text to open a tab in the Detail Viewer as in . The tab remains
open until you click the closure box on the tab or until you close
the viewer.
Editable
value Values appearing in blue type can be changed.
Click the blue text to open a text box. Type the change, and press Enter to immediately apply the change. To view the effect
of the change, choose an appropriate monitoring metric.
Detail
Viewer tab Opens when boldface values are double-clicked.
Tabs appearing in this area provide additional data or operations
that you can modify and immediately apply. The detail tab remains
available until you click the closure box on the tab or until you
close the viewer.
Not all MBeans have operations associated with
them. This tab is grayed out when the selected MBean has no operation
associated with it. The next figure shows an open Operations tab with details about a particular MBean. An explanation follows
the image.
Selected
Operation Name The names are listed with their return type and
number of arguments. By double-clicking a boldface name, the return
type is highlighted and a tab opens in the Detail Viewer containing the operation and one or more editable text boxes. See and .
Operational
detail tab The detail tab remains available until you click
the closure box on the tab or until you close the viewer.
Editable
text box Values appearing in text box can be changed. Type
the change, and press the Operation_Name button to immediately apply the operational change. In
this example, the operational button name is getThreadCpuTime . To view the effect of the change, choose an appropriate monitoring metric.
The MBean Notifications TabNot all MBeans have notifications associated with
them. This tab is grayed out when this information is not present.
The next figure shows an open Notifications tab
with details about the selected MBean. An explanation follows the
image.
Enable
or disable notification Click the check box to enable or disable the notification.
Notification
detail tab When the conditions for the notification are triggered,
messages resulting from the event appear here. The detail tab remains
available until you click the closure box on the tab or until you
close the viewer.
The MBean Information Tab The next figure shows an open Information tab with additional related information about the selected MBean.
An explanation follows the image.
View
classification information Name/Value pairs are given that provide relational
information for the selected MBean.
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