Hi Jaber,
The history variable feature has not implemeneted yet in jbpm 4.3. If you want to store history variable after proces have been deleted, you must store them into your table.
Maciej have implemented this feature in the current trunk. We could try this feature after jbpm 4 releasing.
But I don't think store all of process variables is a good idea. If you want more controlling for the variable data, please create your table and maintain them in your own tables. Please consider about it.