Lecture 9: Data and Database Administration

ISOM3260, Spring 2014

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Where we are now• Database environment

– Introduction to database• Database development process

– steps to develop a database• Conceptual data modeling

– entity-relationship (ER) diagram; enhanced ER• Logical database design

– transforming ER diagram into relations; normalization• Physical database design

– technical specifications of the database• Database implementation

– Structured Query Language (SQL), Advanced SQL• Advanced topics

– data and database administration

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Importance of Data/Database Administration

• Data are a corporate asset – similar to personnel, equipment, and financial assets

• Important assets of the organization need to be managed properly

• Data are stored in databases

• Hence, effective data and database administration provide support for managerial decision-making

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Data/Database Administration

• Data and database administration functions• Managing data security• Backing up databases

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Data/Database Administration

• 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

– headed by a data administrator (DA) a senior-level manager selected from within the organization rather than a

technical computer expert requires high level of both managerial and technical skills

• 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

– Database administrator (DBA) in charge requires broad technical background; managerial skills also critical

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Data Administration Functions• Data policies, procedures, standards

– Policies: e.g., “Every user must have a password”– Procedures: e.g., backup and recovery procedures– Standards: e.g., naming conventions

• Planning– understand the information requirements of the organization and be able

to contribute to the development of the information architecture• Data conflict resolution

– resolve data ownership issues• Internal marketing of data standards

– reduce resistance to change and data ownership problems• Managing the information repository

– contains the metadata– used by users, CASE tools, applications, DBMS

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Database Administration Functions

• Selection of hardware and software• Installing and upgrading the DBMS• Tuning database performance• Improving database query processing performance• Managing data security, privacy, and integrity• Data backup and recovery

Note: Vast majority of time spent by DBA are on tuning database performance

and improving database query processing time.

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Fig 11-1: Functions of data and database administration

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Evolving Approach

• Many organizations are combining the data and database

administration functions– emphasize the capability to build a database quickly, tuning

for maximum performance, and restore to production quickly when problems develop

– using prototyping approach

• DBA expected to maintain required quality levels while

decreasing time required to build a reliable system

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Managing Data Security

• Database Security– protection of the data against accidental or

intentional loss, destruction, or misuse

• Increasingly difficult to manage– access to data become more open through the

Internet and corporate intranets– distributed databases located on client/server

architectures rather than mainframes

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Figure 11-2: Possible locations of data security threats

Both internal and external threats; require firewall and physical security.

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Threats to Data Security

• Accidental losses– 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– data becomes invalid or corrupted

• Loss of availability– sabotage of hardware, networks or applications– virus attack

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Data Management Software Security Features

• Views- restrict user views of the database; CREATE VIEW

• Integrity controls- enforced by the DBMS during querying and updating

• Authorization rules- identify users and restrict the actions they may take against a database- e.g., GRANT SELECT, UPDATE(price) ON PRODUCT_T TO Smith

• User-defined procedures- define additional constraints or limitations in using a database

• Encryption procedures- encode data in an unrecognizable form

• Authentication schemes- positively identify a person attempting to gain access to a database

• Backup databases- facilitate recovery procedures

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Views and Integrity Controls

• Views– subset of the database that is presented to one or more users– user can be given access privilege to view without allowing

access privilege to underlying tables

• Integrity Controls– protect data from unauthorized use and update– Domains: set allowable values– Assertions: enforce database conditions or business rules

(CHECK)– Triggers: more complex than assertions

e.g. recording an entry in a log which users have done what with which data

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Authorization Rules

• Controls incorporated in the DBMS– restrict access to data– restrict actions that people may take when they access data

• Authorization matrix include– subjects, objects, actions, constraints– can be viewed as metadata and stored in the repository

• Authorization tables for subjects• Authorization tables for objects

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Figure 11-4: Authorization matrix

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Figure 11-5(a): Authorization table for subjects (salespersons)

Figure 11-5(b): Authorization table for objects (order records)

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Authentication Schemes• Goal is to obtain a positive identification of the user• Passwords are flawed

– users share them with each other– they get written down, could be copied– automatic logon scripts remove need to explicitly type

them– unencrypted passwords travel the Internet

• Possible solutions– Biometric devices

techniques that measure or detect personal characteristics such as fingerprints, voiceprints, eye pictures, or signature dynamics

– Third-party authentication using secret keys, digital certificates

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Backing Up Databases

• Database recovery is the mechanism for restoring a database quickly and accurately after loss or damage

• Recovery manager– a module of the DBMS which restores the database to a

correct condition when a failure occurs and which resumes processing user requests

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Backup Facilities• An automatic dump facility that produces backup

copy of the entire database• Periodic backup

– e.g. nightly, weekly• Cold backup

– database is shut down during backup• Hot backup

– selected portion of the database is shut down and backed up at a given time

– useful when it is a critical system that must always remain available

• Backups stored in secure, off-site location

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Journalizing Facilities• An audit trail of transactions and database changes• Transaction

– a discrete unit of work that must be completely processed or not processed at all

– e.g. entering a customer order• Transaction log

– record of essential data for each transaction processed against the database

• Database change log– before- and after-images of records that have been modified

by transactions before-image is a copy of record before modification after-image is a copy of record after modification

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Data Characteristics: Status vs. Event DataFigure: Example of DBMS log entry

Status

Status

Event = a database action (create/update/ delete) that results from a transaction

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Figure 11-8: Database audit trail

From the backup and logs, databases can be restored by the recovery manager in case of damage or loss

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Recovery and Restart Procedures

• Switch• Restore/Rerun• Backward Recovery (rollback)• Forward Recovery (rollforward)

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Recovery and Restart Procedures• Switch

– Mirrored databases at least two copies of the database must be kept and updated

simultaneously implemented in RAID 1 systems

– Procedure when a disk failure occurs, system switches to mirrored disk defective disk can be removed and replaced with a new disk

– Advantages no disruption in service; fastest recovery popular as cost of secondary storage has dropped

– Disadvantages does not protect against lost of power or damage to both databases

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Recovery and Restart Procedures• Restore/Rerun

– reprocessing the day’s transactions (up to the point of failure) against the backup copy of the database

– Advantages does not need to create a database change journal no special restart procedures required

– Disadvantages time to reprocess transactions may be long

– Used only as a last resort

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Recovery and Restart Procedures• Backward Recovery (rollback)

– apply before-images of records that have been changed to the database– restore the database to an earlier state– used to reverse the changes made by transactions that have been aborted

or terminated abnormally

• Forward Recovery (rollforward)– starts with an earlier copy of the database– apply after-images (the results of good transactions) to the database– preferable to restore/rerun

do not need to reprocess each transaction only the most recent after-image of a record need to be applied

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Figure 11-9: Basic recovery techniques(a) Rollback

Restore to earlier state

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Figure 11-9(b): Rollforward

Results of good transactions

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Review Questions

• What are the functions of data administration?• What are the functions of database administration?• What are 5 threats to data security?• How 7 DBMS features can help manage data

security?• How to backup databases?• What are 4 recovery and restart procedures?