GWT GAE Datastore Issues

I am currently doing development with GWT and Google Appengine.  It appears that GWT hosted mode (debug) runs in the cache directory structure.  It also copies the file out/exploded/project/WEB-INF/appengine-generated/local_db.bin to the cache directory to run.  I do a lot of testing that I need to empty the datastore, which I do by deleting the for mentioned file.  At first is seems to work fine, then it starts failing to delete the local_db.bin file in the cache directory.  I have to go find the GWT running directory in the cache to make it work.

It seems to be a very bad design to make the running directory in the cache.  For a long time it was a great mystery why I was getting magic reads of a non existent file.  It is also really crappy that I have to go into the cache directory to clean up a run process.  Can someone please explain why this is the case?

Thanks,
Jeffrey