How do I control UL via jcmd VM.log?

Stefan Karlsson stefan.karlsson at
Wed Jan 27 14:23:06 UTC 2016

Hi Thomas,

On 2016-01-27 14:48, Thomas Stüfe wrote:
> Hi all,
> sorry if this is a stupid question. I have trouble figuring out the syntax
> to enable Logging dynamically using jcmd for a life process.
> Whatever argument I hand down to the VM.log command, I
> get java.lang.IllegalArgumentException.
> Examples:
> ./images/jdk/bin/jcmd 12680 VM.log  all
> ./images/jdk/bin/jcmd 12680 VM.log  all=trace
> ./images/jdk/bin/jcmd 12680 'VM.log  all=trace'
> ...
> nothing works.

Try the following to get more help:

./images/jdk/bin/jcmd 12680 VM.log help
Lists, enables, disables or changes a log output configuration.

Impact: Low: No impact


Syntax : VM.log [options]

Options: (options must be specified using the <key> or <key>=<value> syntax)
	output : [optional] The name or index (#<index>) of output to configure. (STRING, no default value)
	output_options : [optional] Options for the output. (STRING, no default value)
	what : [optional] Configures what tags to log. (STRING, no default value)
	decorators : [optional] Configures which decorators to use. Use 'none' or an empty value to remove all. (STRING, no default value)
	disable : [optional] Turns off all logging and clears the log configuration. (BOOLEAN, no default value)
	list : [optional] Lists current log configuration. (BOOLEAN, no default value)

and also:

./images/jdk/bin/jcmd 12680 VM.log list

to see what's currently used.

and then:

./images/jdk/bin/jcmd 12680 VM.log what=all=trace

to change the settings.


> I also looked through but
> did not find a clear answer beside "Everything that can be specified on the
> command line can also be specified dynamically with Diagnostic Commands."
> which did not help much.
> What am I doing wrong?
> Thanks and Kind Regards, Thomas

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