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Data and Database Administration

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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.

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Data Administration Functions

• Data policies, procedures, standards.

• Planning.

• Data conflict (ownership) resolution.

• Internal marketing of DA concepts.

• Managing the data repository.

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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.

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Data Security• Data Security: Protection of the data against accidental or

intentional loss, destruction, or misuse.

• Possible locations of data security threats

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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).

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Data Management Software Security Features

Views or subschemas. Authorization rules.

Fig. 13-3 (right) , 4, 5. User-defined procedures.

E.g. trigger an authorization procedure which asks additional identification questions.

Encryption. Authentication schemes.

Biometric devices.

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Backup and RecoveryBasic Recovery Facilities

Backup Facilities Journalizing Facilities

Fig. 13-6 (right)Transaction Log

- time, records, input values.Database Change Log

- before & after images. Checkpoint Facility

Restart point after a failure. Recovery Manager

Fig 13-6: Database audit trail

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Recovery and Restart Procedures

• Switch - Mirrored databases.

• Restore/Rerun - Reprocess transactions against the backup.

• Transaction Integrity - Commit or abort all transaction changes. (trans boundaries)

• Backward & forward recovery follow….

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Basic recovery techniques(a) Rollback

Backward Recovery - Apply before images.Undo unwanted changes

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(b) RollforwardForward Recovery - Apply after images (preferable to restore/rerun.)

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Types of Database Failure

• Table. 13-1.

• Aborted transactions.

• Incorrect data. (update inaccurate)

• System failure (database intact.)

• Database destruction

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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. 13-8.

• -- refer to html notes --

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Concurrency Control Techniques

• Serializability - Finish one transaction before starting another.

• Locking Mechanisms - Fig. 13-10.– Locking level:

• Database

• Table

• Block or page

• Record

• Field

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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.

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Deadlock• Deadlock - Transactions wait for each other to

release needed resources. Fig. 13-10, 11.

• 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.

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Deadlock• Deadlock Resolution:

– Allow deadlocks to occur.– Mechanisms for detecting and breaking them.

• Resource usage matrix.

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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. 13-12.

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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.

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Data Dictionaries and Repositories

– Passive data dictionary.

– Active data dictionary. (managed by DBMS)

• System catalog.– all DB objects, including data dictionary and user

access info

• Information Repository (CASE tools).• Information Repository Dictionary System (IRDS)

- Manages access- standards for dictionary storage and access.

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Performance tuning the database

• Correct installation• Memory usage• I/O Contention• CPU Usage• Application tuning

– examine SQL