Hi Maciejs,
I debug the application, and it turns out when I do something like start process(ksession.startProcess(..) ), inside DroolsSpringJpaManager these two functions will be invoked:
1. getApplicationScopedPersistenceContext
https://github.com/droolsjbpm/droolsjbpm-integration/blob/5.5.x/drools-container/drools-spring/src/main/java/org/drools/container/spring/beans/persistence/DroolsSpringJpaManager.java#L64-L92
this one will never create new Entity Manager (except for the very first time execution). Which is not safe for Database Restart situation.
2. beginCommandScopedEntityManager
https://github.com/droolsjbpm/droolsjbpm-integration/blob/5.5.x/drools-container/drools-spring/src/main/java/org/drools/container/spring/beans/persistence/DroolsSpringJpaManager.java#L98-L119
while this function will always find that entityManager is closed and then create new Entity Manager which is safe on Database Restart situation.