Data Mgmt Lab_Part_1 - 1 INTRODUCTION TO DATABASE SYSTEMS...

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1 INTRODUCTION TO DATABASE SYSTEMS Exercise 1.1 Why would you choose a database system instead of simply storing data in operating system files? When would it make sense not to use a database system? Answer 1.1 A database is an integrated collection of data, usually so large that it has to be stored on secondary storage devices such as disks or tapes. This data can be maintained as a collection of operating system files, or stored in a DBMS (database management system). The advantages of using a DBMS are: Data independence and efficient access. Database application programs are in- dependent of the details of data representation and storage. The conceptual and external schemas provide independence from physical storage decisions and logical design decisions respectively. In addition, a DBMS provides efficient storage and retrieval mechanisms, including support for very large files, index structures and query optimization. Reduced application development time. Since the DBMS provides several impor- tant functions required by applications, such as concurrency control and crash recovery, high level query facilities, etc., only application-specific code needs to be written. Even this is facilitated by suites of application development tools available from vendors for many database management systems. Data integrity and security. The view mechanism and the authorization facilities of a DBMS provide a powerful access control mechanism. Further, updates to the data that violate the semantics of the data can be detected and rejected by the
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