2. TM 13-1 Copyright © 1999 Addison Wesley Longman, Inc. Data and Database Administration

3. TM 13-2 Copyright © 1999 Addison Wesley Longman, Inc. Definitions Data Administration: A high-level function that is responsible for the overall management of data resources in an organization, including maintaining corporate-wide definitions and standards. Database Administration: A technical function that is responsible for physical database design and for dealing with technical issues such as security enforcement, database performance, and backup and recovery.

4. TM 13-3 Copyright © 1999 Addison Wesley Longman, Inc. Data Administration Functions Data policies, procedures, standards. Planning. Data conflict (ownership) resolution. Internal marketing of DA concepts. Managing the data repository.

5. TM 13-4 Copyright © 1999 Addison Wesley Longman, Inc. Database Administration Functions Selection of hardware and software. Managing data security, privacy, and integrity. Data backup and recovery. Fig. 13-1 is a list of DA and DBA functions.

6. TM 13-5 Copyright © 1999 Addison Wesley Longman, Inc. Data Security Data Security: Protection of the data against accidental or intentional loss, destruction, or misuse. Fig. 13-2.

7. TM 13-6 Copyright © 1999 Addison Wesley Longman, Inc. Possible locations of data security threats

8. TM 13-7 Copyright © 1999 Addison Wesley Longman, Inc. Threats to Data Security Accidental losses attributable to: –Human error. –Software failure. –Hardware failure. Theft and fraud. Improper data access: –Loss of privacy (personal data). –Loss of confidentiality (corporate data). Loss of data integrity. Loss of availability (through, e.g. sabotage).

9. TM 13-8 Copyright © 1999 Addison Wesley Longman, Inc. Data Management Software Security Features ¬Views or subschemas. ­Authorization rules. ­Fig. 13-3, 4, 5. ®User-defined procedures. ®E.g. trigger an authorization procedure which asks additional identification questions. ¯Encryption. °Authentication schemes. °Biometric devices.

10. TM 13-9 Copyright © 1999 Addison Wesley Longman, Inc. Authorization matrix

11. TM 13-10 Copyright © 1999 Addison Wesley Longman, Inc. Backup and Recovery Basic Recovery Facilities ¬Backup Facilities ­Journalizing Facilities ­Fig. 13-6 ­Transaction Log - time, records, input values. ­Database Change Log - before & after images. ®Checkpoint Facility ®Restart point after a failure. ¯Recovery Manager

12. TM 13-11 Copyright © 1999 Addison Wesley Longman, Inc. Database audit trail

13. TM 13-12 Copyright © 1999 Addison Wesley Longman, Inc. Recovery and Restart Procedures Switch - Mirrored databases. Restore/Rerun - Reprocess transactions against the backup. Transaction Integrity - Commit or abort all transaction changes. Backward Recovery (Rollback) - Apply before images. Fig. 13-7. Forward Recovery (Roll Forward) - Apply after images (preferable to restore/rerun.)

14. TM 13-13 Copyright © 1999 Addison Wesley Longman, Inc. Basic recovery techniques (a) Rollback

15. TM 13-14 Copyright © 1999 Addison Wesley Longman, Inc. (b) Rollforward

16. TM 13-15 Copyright © 1999 Addison Wesley Longman, Inc. Types of Database Failure Fig. 13-8. Aborted transactions. Incorrect data. System failure (database intact.) Database destruction

17. TM 13-16 Copyright © 1999 Addison Wesley Longman, Inc. Concurrency Control Concurrency Control - The process of managing simultaneous operations against a database so that data integrity is maintained and the operations do not interfere with each other in a multi-user environment. Lost Update Problem - Fig. 13-9.

18. TM 13-17 Copyright © 1999 Addison Wesley Longman, Inc. Concurrency Control Techniques Serializability - Finish one transaction before starting another. Locking Mechanisms - Fig. 13-10. –Locking level: Database Table Block or page Record Field

19. TM 13-18 Copyright © 1999 Addison Wesley Longman, Inc. Concurrency Control Techniques –Types of locks: Shared lock - Read but not update permitted. Used when just reading to prevent another user from placing an exclusive lock on the record. Exclusive lock - No access permitted. Used when preparing to update.

20. TM 13-19 Copyright © 1999 Addison Wesley Longman, Inc. Deadlock Deadlock - Transactions wait for each other to release needed resources. Fig. 13-11, 12. Deadlock prevention: –Lock all records required at the beginning of a transaction –Two-phase locking protocol Growing phase. Shrinking phase. –May be difficult to determine all needed resources in advance.

21. TM 13-20 Copyright © 1999 Addison Wesley Longman, Inc. Deadlock Deadlock Resolution: –Allow deadlocks to occur. –Mechanisms for detecting and breaking them. Resource usage matrix.

22. TM 13-21 Copyright © 1999 Addison Wesley Longman, Inc. Concurrency Control Techniques Versioning: –Optimistic approach to concurrency control. –Assumption is that simultaneous updates will be infrequent. –Each transaction can attempt an update as it wishes. –The system will reject an update when it senses a conflict. –Fig. 13-13.

23. TM 13-22 Copyright © 1999 Addison Wesley Longman, Inc. Managing Data Quality Data Steward - Liaisons between IT and business units. Five Data Quality Issues: ¬Security policy and disaster recovery. ­Personnel controls. ®Physical access controls. ¯Maintenance controls (hardware & software.) °Data protection and privacy.

24. TM 13-23 Copyright © 1999 Addison Wesley Longman, Inc. Data Dictionaries and Repositories Passive data dictionary. Active data dictionary. Relational catalog. Repository (CASE tools). Information Repository Dictionary System (IRDS) - standards for dictionary storage and access.