MBA 664MBA 664Database ManagementDatabase Management

Dave Salisbury

salisbury@udayton.edu (email)

http://www.davesalisbury.com/ (web site)

SDLC and the database SDLC and the database development processdevelopment processSDLC Database Deliverable

Project ID

Project init

Analysis

Logical design

Physical design

Implementation

Maintenance

Enterprise model

Conceptual Model

Logical model

Data structures and storage plan

Management

Working system

Proper delivery of information not only depends on the capabilities of the computer hardware and software but also on the organization’s ability to manage data as an important resource

Data as a ResourceData as a Resource

How Does IS Manage Data?How Does IS Manage Data?

• Data Administrators: 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 Administrators: 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.

• Data Stewardship: Manages a specific logical data resource for all business functions. Distribute data admin. to those most knowledgeable about specific data

Data Administration FunctionsData Administration Functions

• Data policies, procedures, standards

• Planning

• Data conflict (ownership) resolution

• Internal marketing of DA concepts

• Managing the data repository

Database Administration Database Administration FunctionsFunctions

• Selection of hardware and software

• Managing data security, privacy, and integrity

• Data backup and recovery

• Figure 12.1 offers a list of DA and DBA functions

Threats to Data SecurityThreats 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).

Data security threat sourcesData security threat sources

Database Security FeaturesDatabase Security Features

• Protection of the database against accidental or intentional loss, destruction or misuse– Views– Authorization rules– User-defined procedures– Encryption procedures– Authentication schemes

Database Security FeaturesDatabase Security Features

• Views– Restrict user access to data– Various ways to get around so not

sufficient measure

• Authorization Rules– Controls embedded in DBMS that restrict

user access to data and user actions that can be enacted on data

• Who can update? Insert? Read?

Authorization matrixAuthorization matrix

Database Security FeaturesDatabase Security Features

• User-Defined Procedures– Allows system designers to add other security

features• Passwords• Valid procedure name

• Encryption– Coding of data so that it cannot be read by

humans• Financial and military data• WWW issues• Government ability to decode all encryption schemes

Database Security FeaturesDatabase Security Features

• Authentication Schemes– How to positively identify that person trying

to gain access to a computer resource is “that” person

• Biometric devices--measure fingerprints, voice prints, retina prints

• Smart card would have biometric data embedded

Database FailuresDatabase Failures

• Aborted Transactions– A transaction is not completed

• Incorrect Data– data entry error, calculation error, coding

error• System Failure

– Component failure, power failure• Database Destruction

– drive failure, disaster recovery

Database Recovery and Basic Database Recovery and Basic Recovery FacilitiesRecovery Facilities

• Backup facilities• Periodic backup copies of entire DB

• Journalizing facilities• Maintain an audit trail of transactions and DB changes

• Checkpoint facilities• DBMS suspends all processing and synchronizes files

and journals

• Recovery manager• Allows the DBMS to restore the DB to correct condition

and restart

Recovery and Restart Recovery and Restart ProceduresProcedures

• Restore/Rerun– Reprocess the day’s transactions up to the

point of failure against a backup copy of the database

– Simple– Time to reprocess may be prohibitive– Sequencing of transactions may be

different than when originally run • withdrawal posted prior to deposit

Recovery and Restart Recovery and Restart ProceduresProcedures

• Transaction Integrity– Transaction changes are not made to the

DB until the entire transaction has been completed and the changes are committed

– If transaction fails at any point, the transaction is aborted

Recovery and Restart Recovery and Restart ProceduresProcedures

• Backward Recovery (Rollback)– Back out of unwanted changes to the database– Used to reverse the changes that have been made

to transactions that have been aborted

• Forward Recovery (Rollforward)– Use an earlier copy of the DB and apply after

images of good transactions– More accurate and faster than restore/rerun

Basic recovery techniquesBasic recovery techniques(a) Rollback(a) Rollback

(b) Rollforward(b) Rollforward

Concurrency ControlConcurrency Control

• Concerns with preventing loss of data integrity due to interference between users in a multi-user environment– Pessimistic approach: interference will always

occur so we LOCK records– Optimistic approach: interference will rarely occur

so we VERSION records

• Multiple concurrent updates to a database can lead to lost updates and therefore to errors

Lost Update ExampleLost Update ExampleTime

John

Read account Balance(balance = $1,000)

.

.

.Withdraw $200(balance = $800

.

.

.Write account balance

(balance = $800)

Marsha

Read account balance(balance = $1,000)

.

.

.Withdraw $300

(balance = $700)...

Write account balance(balance = $700)

ERROR

LockingLocking

• Deny access of data to other users while an update is underway

• Locking level (granularity)– Database - during backups– Table - during batch updates– Block or page - generally not used– Record - Often used– Field - Useful when only one field is likely

to change

Types of LocksTypes of Locks

• Shared– Allows others to read, but not write– Prevents others from putting Exclusive lock

on the record

• Exclusive– Denies other access to the record (even

read)– Necessary when updating the record

DeadlockDeadlock(aka: Deadly Embrace)(aka: Deadly Embrace)

• Two or more transactions have placed locks on record(s) that the others need.

• Each waits for the other(s) to release• Requires DBMS intervention

– Prevention, often not practical– Resolution, common solution

• Detects deadlock and backs one or more transactions out, lets one finish, then restarts next transaction.

VersioningVersioning• Each transaction is restricted to a view of the

database as of the transaction start time.• When transaction modifies a record, the

DBMS creates a new version of record instead of overwriting old record

• Changes to 2 identical views simultaneously– First change (according to time stamp) is enacted– Second change is informed of conflict and

transaction must be performed again

VersioningVersioningJohn

Read account Balance(balance = $1,000)

.

.

.Withdraw $200(balance = $800

.

.

.Commit

Marsha

Read account balance(balance = $1,000)

.

.

.Attempt to withdraw $300(Denied - balance update

conflict)..

Rollback

Restart transaction

Managing Data QualityManaging Data Quality

• Security policy and disaster recovery

• Personnel controls

• Physical access controls

• Maintenance controls (hardware & software)

• Data protection and privacy