Java Plug-in and Java Web Start deployment products should have the common environment variable to override profile paths deployment.user.profile and deployment.system.profile . Currently ,It is always a default location, where as in plug-in . USER_JPI_PROFILE variable overrides the profile paths(cache location, tracing etc ) are based on the profile path.

ATF(plug-in automation framework) currently depend on this variable to unique generation of tracing at central location.

As this is consolidation , overriding profile should be the same across
all deployment products ( Java Plug-in and Java Web start) , should provide a
environment variable as mentioned in the engineering specifications.
sec 2.1.3

http://j2se.east/deployment/specs/deploy/1.5/unifoed_configuration.html.

This feature might also be useful in the debugging purpose.