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Data and Database Administration

Chapter 12

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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.

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STAGES IN THE LIFE CYCLE OF A DATABASE SYSTEM

• database planning

• database analysis

• database design

• database implementation

• operation and maintenance

• growth and change

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Data Dictionaries and Repositories

• Passive data dictionary– used by people

• Active data dictionary– CASE tool (development)– metadata (production)

• Relational catalog.

• Repository (CASE tools).

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Information Repository Dictionary System (IRDS)

• A computer software tool that is used to manage and control access to the information repository.

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Information Repository

• Stores metadata that describes an organization’s data and data processing resources.

• Manages the total information processing environment.

• Combines information about an organization’s business information and its application portfolio.

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DBMS ENGINE

• The central component of a DMS.

• Provides access to the repository and the database and coordinates all of the other functional elements of the DMS.

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Interface Subsystem

• Provides facilities for users and applications to access the various components of the DBMS.

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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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Database ManagementSubsystems

• Performance Management Subsystem

• Data Integrity Management Subsystem

• Backup and Recovery Subsystem

• Application Development Subsystem

• Security Management Subsystem

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Backup and RecoveryBasic Recovery Facilities

Backup FacilitiesJournalizing Facilities

Fig. 13-6Transaction Log - time, records, input values.Database Change Log - before & after images.

Checkpoint FacilityRestart point after a failure.

Recovery Manager

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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.

• Backward Recovery (Rollback) - Apply before images. Fig. 13-7.

• Forward Recovery (Roll Forward) - Apply after images (preferable to restore/rerun.)

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Basic recovery techniques(a) Rollback

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(b) Rollforward

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Types of Database Failure

• Fig. 13-8.

• Aborted transactions.

• Incorrect data.

• 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. 13-9.

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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. 13-11, 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.

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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. 13-13.