Exercise 1.6 Scrooge McNugget wants to store information (names, addresses, descriptions of embarrassing moments, etc.) about the many ducks on his payroll. Not surprisingly, the volume of data compels him to buy a database system. To save money, he wants to buy one with the fewest possible features, and he plans to run it as a stand-alone application on his PC clone. Of course, Scrooge does not plan to share his list with anyone. Indicate which of the following DBMS features Scrooge should pay for; in each case also indicate why Scrooge should (or should not) pay for that feature in the system he buys. 1. A security facility. 2. Concurrency control. 3. Crash recovery. 4. A view mechanism. 5. A query language. Answer 1.6 Answer omitted

Exercise 21.15 Consider a heterogeneous distributed DBMS. 1. Define the terms multidatabase system and gateway. 2. Describe how queries that span multiple sites are executed in a multidatabase system. Explain the role of the gateway with respect to catalog interfaces, query optimization, and query execution. 3. Describe how transactions that update data at multiple sites are executed in a multidatabase system. Explain the role of the gateway with respect to lock management, distributed deadlock detection, Two-Phase Commit, and recovery. 4. Schemas at different sites in a multidatabase system are probably designed independently. This situation can lead to semantic heterogeneity; that is, units of measure may differ across sites (e.g., inches versus centimeters), relations containing essentially the same kind of information (e.g., employee salaries and ages) may have slightly different schemas, and so on. What impact does this heterogeneity have on the end user? In particular, comment on the concept of distributed data independence in such a system. Parallel and Distributed Databases 215 Answer 21.15 1. A multi-database system (a.k.a.