In context of deadlock prevention in DBMS, wait-die and wound-wait schemes are…

In deadlock prevention, wait-die and wound-wait are both preemptive techniques. In the wait-die scheme, if a younger transaction requests a resource held by an older one, the younger transaction waits. If the older transaction requests a resource held by the younger one, the older transaction is rolled back (dies). This rollback of the older transaction is a form of preemption. In the wound-wait scheme, if a younger transaction requests a resource held by an older one, the younger transaction is rolled back (wounded). If the older transaction requests a resource held by the younger one, the older transaction waits. This rollback of the younger transaction is also a form of preemption. Therefore, both schemes involve preemption and are preemptive techniques.