Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Data and Database Administration Copyright © 1999 Addison Wesley Longman, Inc. TM 13-1 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-2 Data Administration Functions • • • • • Data policies, procedures, standards. Planning. Data conflict (ownership) resolution. Internal marketing of DA concepts. Managing the data repository. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-3 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-4 Data Security • Data Security: Protection of the data against accidental or intentional loss, destruction, or misuse. • Fig. 13-2. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-5 Possible locations of data security threats Copyright © 1999 Addison Wesley Longman, Inc. TM 13-6 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). Copyright © 1999 Addison Wesley Longman, Inc. TM 13-7 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-8 Authorization matrix Copyright © 1999 Addison Wesley Longman, Inc. TM 13-9 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 Copyright © 1999 Addison Wesley Longman, Inc. TM 13-10 Database audit trail Copyright © 1999 Addison Wesley Longman, Inc. TM 13-11 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.) Copyright © 1999 Addison Wesley Longman, Inc. TM 13-12 Basic recovery techniques (a) Rollback Copyright © 1999 Addison Wesley Longman, Inc. TM 13-13 (b) Rollforward Copyright © 1999 Addison Wesley Longman, Inc. TM 13-14 Types of Database Failure • • • • • Fig. 13-8. Aborted transactions. Incorrect data. System failure (database intact.) Database destruction Copyright © 1999 Addison Wesley Longman, Inc. TM 13-15 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-16 Concurrency Control Techniques • Serializability - Finish one transaction before starting another. • Locking Mechanisms - Fig. 13-10. – Locking level: • • • • • Database Table Block or page Record Field Copyright © 1999 Addison Wesley Longman, Inc. TM 13-17 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-18 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-19 Deadlock • Deadlock Resolution: – Allow deadlocks to occur. – Mechanisms for detecting and breaking them. • Resource usage matrix. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-20 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-21 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-22 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. Copyright © 1999 Addison Wesley Longman, Inc. TM 13-23