Evaluate:
a.When transactions T1 and T2 are in a deadlock, one of the transactions will eventually implement to completion and let the other one continue implementation.
b. When an inform to the database takes place, the time of the update, the values of the data previous to and after the update, and the type of lock used are recorded in the transaction log.
c. To restore a database using the instant update approach, both undo and redo operations may be essential, while with the deferred update approach only redo operations are used.