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Chapter 12 Managing Multi-user Databases David M. Kroenke Database Processing © 2000 Prentice Hall.

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Presentation on theme: "Chapter 12 Managing Multi-user Databases David M. Kroenke Database Processing © 2000 Prentice Hall."— Presentation transcript:

1 Chapter 12 Managing Multi-user Databases David M. Kroenke Database Processing © 2000 Prentice Hall

2 Chapter 12 © 2000 Prentice Hall Multi-User Issues Concurrency Control Database Reliability Database Security Database Administration Page 307

3 Chapter 12 © 2000 Prentice Hall Common Multi-User DBMS Windows 2000 –Access 2000 –SQL Server –ORACLE UNIX –ORACLE –Sybase –Informix Page 307

4 Chapter 12 © 2000 Prentice Hall Concurrency Control “making sure that one user’s work does not inappropriately influence another’s” The need for atomic transactions “logical work performed as a unit” Page 308

5 Chapter 12 © 2000 Prentice Hall Concurrent Processing Problems Lost update problem Inconsistent read problem Page 312

6 Chapter 12 © 2000 Prentice Hall Remedy for inconsistencies caused by concurrent processing Resource Locking “disallow sharing by locking data that are retrieved for update” Page 312

7 Chapter 12 © 2000 Prentice Hall Lock Terminology Implicit locks placed by the DBMS Explicit locks placed by command Lock granularity the size of the lock Exclusive lock from access of any type Shared lock from change but not read Page 312

8 Chapter 12 © 2000 Prentice Hall Serializable Transactions “a scheme for processing concurrent transactions” Strategies –two-phased locking –COMMIT and ROLLBACK commands Page 313

9 Chapter 12 © 2000 Prentice Hall Deadlock “deadly embrace”; each transaction waiting for a resource that the other person has locked Page 314

10 Chapter 12 © 2000 Prentice Hall Lock Styles Optimistic assumption is made that no conflict will occur Pessimistic assumption is made that conflict will occur Page 314

11 Transaction Isolation Levels Page 317 Figure 12-8 © 2000 Prentice Hall

12 Summary of Cursor Types Page 319 Figure 12-9 © 2000 Prentice Hall

13 Chapter 12 © 2000 Prentice Hall Database Recovery Via Reprocessing Via Rollback/Rollforward Page 320

14 Chapter 12 © 2000 Prentice Hall Recovery Terminology Log records of the data changes in chronological order Before-images/After-images copy of every record before / after it was changed Checkpoint a point of synchronization between the database and the transaction log Page 321

15 Database Security Page 324 Figure © 2000 Prentice Hall

16 Model of ORACLE Security Page 325 Figure 12-14a © 2000 Prentice Hall

17 Model of SQL Server Security Page 327 Figure 12-15a © 2000 Prentice Hall

18 Chapter 12 © 2000 Prentice Hall Database Administration DBA database administrator –manages the database structure –manages data activity –manages the DBMS –manages the data repository Page 329

19 Chapter 12 © 2000 Prentice Hall Managing the Database Structure Configuration Control Documentation Page 330

20 Managing the Database Structure Page 331 Figure © 2000 Prentice Hall

21 Chapter 12 © 2000 Prentice Hall Managing Data Activity Data dictionary names and formats of the data items, and their relationships Data proponents key database users Page 331

22 Managing Data Activity Page 332 Figure © 2000 Prentice Hall

23 Managing the DBMS Page 333 Figure © 2000 Prentice Hall

24 Chapter 12 © 2000 Prentice Hall Managing the Data Repository Data repositories collections of metadata about databases, database applications, Web pages, users, and other application components –active –passive Page 334


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