 <blockquote> <p>increasing the heap size</p> </blockquote> <p>is the way to go. But you also have to check how to do a distribute test; because 12000 is a big test that can't be run only in one machine alone; it is not a good practice.</p> <p><a href="http://jmeter.apache.org/usermanual/jmeter_distributed_testing_step_by_step.pdf" rel="nofollow">http://jmeter.apache.org/usermanual/jmeter_distributed_testing_step_by_step.pdf</a></p>