Define Deadlock prevention

These protocols make sure that the system will never enter a deadlock state. There are two methods to deadlock prevention. One approach makes sure that no cyclic waits can take place by ordering the requests for locks, or requiring all locks to be obtained together. The other method is closer to deadlock recovery, and carries out transaction rollback in place of waiting for a lock, while the wait could potentially result in a deadlock. In this approach two timestamp based methods are there: wait - die and wound - wait. In wait -die, the older transaction is permitted to wait if it needs data from older transaction. In wound - wait, the younger transaction is rolled back if it requires data from older transaction if older transaction requires data currently held by a younger transaction, though younger transaction is allowed wait if it requires data from older transaction.