1.9 Answer the following questions:
1. What is a transaction?
2. Why does a DBMS interleave the action of different transactions instead of executing transactions one after the other?
3. What must a user guarantee with respect to a transaction and database consistency?
What should a DBMS guarantee with respect to concurrent execution of several transactions and database consistency?
4. Explain the strict two-phase locking protocol.
5. What is the WAL property, and why is it important?