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Reference Scanner
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Frequently Asked Questions
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Reference Scanner Frequently Asked Questions
How much memory does Reference Scanner need?
Runtime and Snapshot information will be created in the java heap.
The currently used memory will be displayed in the progress bar. If the progress indicator
is at the end of the bar then more memory is required to render the
information into html format.
The 'java -Xmx???M' option specifies how much maximum heap your application
does get. If '-Xmx' is set to low then the application will hang for a while and ends
with an 'OutOfMemory' Exception finally. A safe value is your application heap
(after forced gc) x 2 .
How do I get rid of the snapshots again?
You can go to the Start page of Reference Scanner - by the navigation bar
upper left corner - and do a 'Clear Snapshots' there.
Or - you simply log out from Reference Scanner.
Which options can make sense to turn them off?
For heap snapshots:
You can use a filter in heap snapshots. You can turn of options like bar graph.
For call graph recording:
You can work with include /exclude options for packages. See usage.
How can I start Reference Scanner twice?
Not at the same port. In this case the later started instance sends a stop
request to the first started one.
You can control the stop behaviour with the following option:
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<!-- ${user.home}/.jb2works.com/refscan/ScannerConfig.xml -->
<stop-policy kill="false"/>
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This option defaults to 'false' which means that only the Reference Scanner port
will be closed but the profiled application will stay alive.
If 'true' then the application will be closed by calling System.exit(0).
How do I change the port of Reference Scanner?
You can set the jvm argument '-Drefscan.port=xxxx'.
How can I suppress the log messages to the console at startup?
Yes, you can set the following option:
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<!-- ${user.home}/.jb2works.com/refscan/ScannerConfig.xml -->
<be-quiet value="true"/>
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This will suppress the console output of Reference Scanner.
Does Reference Scanner find all kinds of memory leaks?
No. Leaks in native jvm functions will not be detected.
Can you tell me an example for a native memory leak?
Yes. For example you can forget to dispose() a JFrame.
Can I run Reference Scanner when I use a security manager?
This depends on the restrictions which the security manager applies to the
execution of java code. See security policy below.
Which security policy settings are required?
Reference Scanner must be able to
override the java.lang.Field access flag via reflection,
to read the system property 'user.home',
to create, read, write, delete files on local file system,
to run a java.net.ServerSocket on Reference Scanners port.
By default these settings are enabled in the JRE.
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