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  1. 1. Data and Database Administration Chapter 12
  2. 2. Definitions <ul><li>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. </li></ul><ul><li>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 . </li></ul>
  3. 3. Data Administration Functions <ul><li>Data policies, procedures, standards. </li></ul><ul><li>Planning. </li></ul><ul><li>Data conflict (ownership) resolution. </li></ul><ul><li>Internal marketing of DA concepts. </li></ul><ul><li>Managing the data repository. </li></ul>
  4. 4. Database Administration Functions <ul><li>Selection of hardware and software. </li></ul><ul><li>Managing data security, privacy, and integrity. </li></ul><ul><li>Data backup and recovery. </li></ul>
  5. 5. STAGES IN THE LIFE CYCLE OF A DATABASE SYSTEM <ul><li>database planning </li></ul><ul><li>database analysis </li></ul><ul><li>database design </li></ul><ul><li>database implementation </li></ul><ul><li>operation and maintenance </li></ul><ul><li>growth and change </li></ul>
  6. 6. Data Dictionaries and Repositories <ul><li>Passive data dictionary </li></ul><ul><ul><li>used by people </li></ul></ul><ul><li>Active data dictionary </li></ul><ul><ul><li>CASE tool (development) </li></ul></ul><ul><ul><li>metadata (production) </li></ul></ul><ul><li>Relational catalog. </li></ul><ul><li>Repository (CASE tools). </li></ul>
  7. 7. Information Repository Dictionary System (IRDS) <ul><li>A computer software tool that is used to manage and control access to the information repository. </li></ul>
  8. 8. Information Repository <ul><li>Stores metadata that describes an organization’s data and data processing resources. </li></ul><ul><li>Manages the total information processing environment. </li></ul><ul><li>Combines information about an organization’s business information and its application portfolio. </li></ul>
  9. 9. DBMS ENGINE <ul><li>The central component of a DMS. </li></ul><ul><li>Provides access to the repository and the database and coordinates all of the other functional elements of the DMS. </li></ul>
  10. 10. Interface Subsystem <ul><li>Provides facilities for users and applications to access the various components of the DBMS. </li></ul>
  11. 11. Managing Data Quality <ul><li>Data Steward - Liaisons between IT and business units. </li></ul><ul><li>Five Data Quality Issues: </li></ul><ul><ul><li>Security policy and disaster recovery. </li></ul></ul><ul><ul><li>Personnel controls. </li></ul></ul><ul><ul><li>Physical access controls. </li></ul></ul><ul><ul><li>Maintenance controls (hardware & software.) </li></ul></ul><ul><ul><li>Data protection and privacy. </li></ul></ul>
  12. 12. Database Management Subsystems <ul><li>Performance Management Subsystem </li></ul><ul><li>Data Integrity Management Subsystem </li></ul><ul><li>Backup and Recovery Subsystem </li></ul><ul><li>Application Development Subsystem </li></ul><ul><li>Security Management Subsystem </li></ul>
  13. 13. Backup and Recovery Basic Recovery Facilities <ul><li>Backup Facilities </li></ul><ul><li>Journalizing Facilities </li></ul><ul><ul><li>Fig. 13-6 </li></ul></ul><ul><ul><li>Transaction Log - time, records, input values. </li></ul></ul><ul><ul><li>Database Change Log - before & after images. </li></ul></ul><ul><li>Checkpoint Facility </li></ul><ul><ul><li>Restart point after a failure. </li></ul></ul><ul><li>Recovery Manager </li></ul>
  14. 14. Database audit trail
  15. 15. Recovery and Restart Procedures <ul><li>Switch - Mirrored databases. </li></ul><ul><li>Restore/Rerun - Reprocess transactions against the backup. </li></ul><ul><li>Transaction Integrity - Commit or abort all transaction changes. </li></ul><ul><li>Backward Recovery (Rollback) - Apply before images. Fig. 13-7. </li></ul><ul><li>Forward Recovery (Roll Forward) - Apply after images (preferable to restore/rerun.) </li></ul>
  16. 16. Basic recovery techniques (a) Rollback
  17. 17. (b) Rollforward
  18. 18. Types of Database Failure <ul><li>Fig. 13-8. </li></ul><ul><li>Aborted transactions. </li></ul><ul><li>Incorrect data. </li></ul><ul><li>System failure (database intact.) </li></ul><ul><li>Database destruction </li></ul>
  19. 19. Concurrency Control <ul><li>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. </li></ul><ul><li>Lost Update Problem - Fig. 13-9. </li></ul>
  20. 20. Concurrency Control Techniques <ul><li>Serializability - Finish one transaction before starting another. </li></ul><ul><li>Locking Mechanisms - Fig. 13-10. </li></ul><ul><ul><li>Locking level: </li></ul></ul><ul><ul><ul><li>Database </li></ul></ul></ul><ul><ul><ul><li>Table </li></ul></ul></ul><ul><ul><ul><li>Block or page </li></ul></ul></ul><ul><ul><ul><li>Record </li></ul></ul></ul><ul><ul><ul><li>Field </li></ul></ul></ul>
  21. 21. Concurrency Control Techniques <ul><ul><li>Types of locks: </li></ul></ul><ul><ul><ul><li>Shared lock - Read but not update permitted. Used when just reading to prevent another user from placing an exclusive lock on the record. </li></ul></ul></ul><ul><ul><ul><li>Exclusive lock - No access permitted. Used when preparing to update. </li></ul></ul></ul>
  22. 22. Deadlock <ul><li>Deadlock - Transactions wait for each other to release needed resources. Fig. 13-11, 12. </li></ul><ul><li>Deadlock prevention: </li></ul><ul><ul><li>Lock all records required at the beginning of a transaction </li></ul></ul><ul><ul><li>Two-phase locking protocol </li></ul></ul><ul><ul><ul><li>Growing phase. </li></ul></ul></ul><ul><ul><ul><li>Shrinking phase. </li></ul></ul></ul><ul><ul><li>May be difficult to determine all needed resources in advance. </li></ul></ul>
  23. 23. Deadlock <ul><li>Deadlock Resolution: </li></ul><ul><ul><li>Allow deadlocks to occur. </li></ul></ul><ul><ul><li>Mechanisms for detecting and breaking them. </li></ul></ul><ul><ul><ul><li>Resource usage matrix. </li></ul></ul></ul>
  24. 24. Concurrency Control Techniques <ul><li>Versioning: </li></ul><ul><ul><li>Optimistic approach to concurrency control. </li></ul></ul><ul><ul><li>Assumption is that simultaneous updates will be infrequent. </li></ul></ul><ul><ul><li>Each transaction can attempt an update as it wishes. </li></ul></ul><ul><ul><li>The system will reject an update when it senses a conflict. </li></ul></ul><ul><ul><li>Fig. 13-13. </li></ul></ul>