© 2009 Pearson Education, Inc.  Publishing as Prentice © 2009 Pearson Education, Inc.  Publishing as Prentice HallHall 11

Chapter 13:Chapter 13: Data and Database Data and Database

AdministrationAdministrationModern Database ManagementModern Database Management

99thth Edition EditionJeffrey A. Hoffer, Mary B. Prescott, Jeffrey A. Hoffer, Mary B. Prescott,

Heikki TopiHeikki Topi

Chapter 13 22

ObjectivesObjectives• Definition of termsDefinition of terms• List functions and roles of data/database administrationList functions and roles of data/database administration• Describe role of data dictionaries and information Describe role of data dictionaries and information

repositoriesrepositories• Compare optimistic and pessimistic concurrency controlCompare optimistic and pessimistic concurrency control• Describe problems and techniques for data securityDescribe problems and techniques for data security• Describe problems and techniques for data recoveryDescribe problems and techniques for data recovery• Describe database tuning issues and list areas where changes Describe database tuning issues and list areas where changes

can be done to tune the databasecan be done to tune the database• Describe importance and measures of data availabilityDescribe importance and measures of data availability

Chapter 13 33

Traditional Administration DefinitionsTraditional Administration Definitions

• Data AdministrationData Administration:: A high-level function that is A high-level function that is responsible for the overall management of data responsible for the overall management of data resources in an organization, including maintaining resources in an organization, including maintaining corporate-wide definitions and standardscorporate-wide definitions and standards

• Database AdministrationDatabase Administration:: A technical function that A technical function that is responsible for physical database design and for is responsible for physical database design and for dealing with technical issues such as security dealing with technical issues such as security enforcement, database performance, and backup enforcement, database performance, and backup and recoveryand recovery

Chapter 13 44

Traditional Data Administration Traditional Data Administration FunctionsFunctions

• Data policies, procedures, standardsData policies, procedures, standards• PlanningPlanning• Data conflict (ownership) resolutionData conflict (ownership) resolution• Managing the information repositoryManaging the information repository• Internal marketing of DA conceptsInternal marketing of DA concepts

Chapter 13 55

Traditional Database Traditional Database Administration FunctionsAdministration Functions

• Selection of DBMS and software toolsSelection of DBMS and software tools• Installing/upgrading DBMSInstalling/upgrading DBMS• Tuning database performanceTuning database performance• Improving query processing performanceImproving query processing performance• Managing data security, privacy, and integrityManaging data security, privacy, and integrity• Data backup and recoveryData backup and recovery

Chapter 13 66

Evolving Approaches to Data Evolving Approaches to Data AdministrationAdministration

• Blend data and database administration into one roleBlend data and database administration into one role• Fast-track development–monitoring development process Fast-track development–monitoring development process

(planning, analysis, design, implementation, maintenance)(planning, analysis, design, implementation, maintenance)• Procedural DBAs–managing quality of triggers and stored Procedural DBAs–managing quality of triggers and stored

proceduresprocedures• eDBA–managing Internet-enabled database applicationseDBA–managing Internet-enabled database applications• PDA DBA–data synchronization and personal database PDA DBA–data synchronization and personal database

managementmanagement• Data warehouse administrationData warehouse administration

Chapter 13 77

Data Warehouse AdministrationData Warehouse Administration• New role, coming with the growth in data New role, coming with the growth in data

warehouseswarehouses• Similar to DA/DBA rolesSimilar to DA/DBA roles• Emphasis on integration and coordination of Emphasis on integration and coordination of

metadata/data across many data sourcesmetadata/data across many data sources• Specific roles:Specific roles:

– Support DSS applicationsSupport DSS applications– Manage data warehouse growthManage data warehouse growth– Establish service level agreements regarding data Establish service level agreements regarding data

warehouses and data martswarehouses and data marts

Chapter 13 88

Open Source DBMSsOpen Source DBMSs• An alternative to proprietary packages such as Oracle, An alternative to proprietary packages such as Oracle,

Microsoft SQL Server, or Microsoft AccessMicrosoft SQL Server, or Microsoft Access• mySQL is an example of an open-source DBMSmySQL is an example of an open-source DBMS• Less expensive than proprietary packagesLess expensive than proprietary packages• Source code available, for modificationSource code available, for modification• Absence of complete documentationAbsence of complete documentation• Ambiguous licensing concernsAmbiguous licensing concerns• Not as feature-rich as proprietary DBMSsNot as feature-rich as proprietary DBMSs• Vendors may not have certification programsVendors may not have certification programs

Chapter 13 99

Figure 13-2 Data modeling responsibilities

Chapter 13 1010

Database SecurityDatabase Security

• Database Security:Database Security: Protection of the Protection of the data against accidental or intentional data against accidental or intentional loss, destruction, or misuseloss, destruction, or misuse

• Increased difficulty due to Internet Increased difficulty due to Internet access and client/server technologiesaccess and client/server technologies

Chapter 13 1111

Figure 13-3 Possible locations of data security threats

Chapter 13 1212

Threats to Data SecurityThreats to Data Security• Accidental losses attributable to:Accidental losses attributable to:

– Human errorHuman error– Software failureSoftware failure– Hardware failureHardware failure

• Theft and fraudTheft and fraud• Improper data access:Improper data access:

– Loss of privacy (personal data)Loss of privacy (personal data)– Loss of confidentiality (corporate data)Loss of confidentiality (corporate data)

• Loss of data integrityLoss of data integrity• Loss of availability (through, e.g. sabotage)Loss of availability (through, e.g. sabotage)

Chapter 13 1313

Figure 13-4 Establishing Internet Security

Chapter 13 1414

Web SecurityWeb Security• Static HTML files are easy to secureStatic HTML files are easy to secure

– Standard database access controlsStandard database access controls– Place Web files in protected directories on serverPlace Web files in protected directories on server

• Dynamic pages are harderDynamic pages are harder– Control of CGI scriptsControl of CGI scripts– User authenticationUser authentication– Session securitySession security– SSL for encryptionSSL for encryption– Restrict number of users and open portsRestrict number of users and open ports– Remove unnecessary programs Remove unnecessary programs

Chapter 13 1515

W3C Web Privacy StandardW3C Web Privacy Standard• Platform for Privacy Protection (P3P) Platform for Privacy Protection (P3P) • Addresses the following:Addresses the following:

– Who collects dataWho collects data– What data is collected and for what purposeWhat data is collected and for what purpose– Who is data shared withWho is data shared with– Can users control access to their dataCan users control access to their data– How are disputes resolvedHow are disputes resolved– Policies for retaining dataPolicies for retaining data– Where are policies kept and how can they be accessedWhere are policies kept and how can they be accessed

Chapter 13 1616

Database Software Security Database Software Security FeaturesFeatures

• Views or subschemasViews or subschemas• Integrity controlsIntegrity controls• Authorization rulesAuthorization rules• User-defined proceduresUser-defined procedures• EncryptionEncryption• Authentication schemesAuthentication schemes• Backup, journalizing, and checkpointingBackup, journalizing, and checkpointing

Chapter 13 1717

Views and Integrity ControlsViews and Integrity Controls

• ViewsViews– Subset of the database that is presented to one or more Subset of the database that is presented to one or more

usersusers– User can be given access privilege to view without User can be given access privilege to view without

allowing access privilege to underlying tablesallowing access privilege to underlying tables

• Integrity ControlsIntegrity Controls– Protect data from unauthorized useProtect data from unauthorized use– Domains–set allowable valuesDomains–set allowable values– Assertions–enforce database conditionsAssertions–enforce database conditions

Chapter 13 1818

Authorization RulesAuthorization Rules• Controls incorporated in the data management Controls incorporated in the data management

systemsystem• Restrict: Restrict:

– access to dataaccess to data– actions that people can take on dataactions that people can take on data

• Authorization matrix for:Authorization matrix for:– SubjectsSubjects– ObjectsObjects– ActionsActions– ConstraintsConstraints

Chapter 13 1919

Figure 13-5 Authorization matrix

Chapter 13 2020

Some DBMSs also provide capabilities for user-defined procedures to customize the authorization process

Figure 13-6a Authorization table for subjects (salespeople)

Figure 13-6b Authorization table for objects (orders)

Figure 13-7 Oracle privileges

Implementing authorization rules

Chapter 13 2121

Encryption – the coding or scrambling of data so that humans cannot read them

Secure Sockets Layer (SSL) is a popular encryption scheme for TCP/IP connections

Figure 13-8 Basic two-key encryption

Chapter 13 2222

Authentication SchemesAuthentication Schemes• Goal – obtain a Goal – obtain a positivepositive identification of the identification of the

useruser• Passwords: First line of defensePasswords: First line of defense

– Should be at least 8 characters longShould be at least 8 characters long– Should combine alphabetic and numeric dataShould combine alphabetic and numeric data– Should not be complete words or personal Should not be complete words or personal

informationinformation– Should be changed frequentlyShould be changed frequently

Chapter 13 2323

Authentication Schemes (cont.)Authentication Schemes (cont.)• Strong AuthenticationStrong Authentication

– Passwords are flawed:Passwords are flawed:• Users share them with each otherUsers share them with each other• They get written down, could be copiedThey get written down, could be copied• Automatic logon scripts remove need to explicitly type them inAutomatic logon scripts remove need to explicitly type them in• Unencrypted passwords travel the InternetUnencrypted passwords travel the Internet

• Possible solutions:Possible solutions:– Two factor–e.g. smart card plus PINTwo factor–e.g. smart card plus PIN– Three factor–e.g. smart card, biometric, PINThree factor–e.g. smart card, biometric, PIN– Biometric devices–use of fingerprints, retinal scans, etc. for Biometric devices–use of fingerprints, retinal scans, etc. for

positive IDpositive ID– Third-party mediated authentication–using secret keys, digital Third-party mediated authentication–using secret keys, digital

certificatescertificates

Chapter 13 2424

Security Policies and ProceduresSecurity Policies and Procedures

• Personnel controlsPersonnel controls– Hiring practices, employee monitoring, security trainingHiring practices, employee monitoring, security training

• Physical access controlsPhysical access controls– Equipment locking, check-out procedures, screen Equipment locking, check-out procedures, screen

placementplacement• Maintenance controlsMaintenance controls

– Maintenance agreements, access to source code, quality Maintenance agreements, access to source code, quality and availability standardsand availability standards

• Data privacy controlsData privacy controls– Adherence to privacy legislation, access rulesAdherence to privacy legislation, access rules

Chapter 13 2525

Database RecoveryDatabase Recovery

Mechanism for restoring a database quickly Mechanism for restoring a database quickly and accurately after loss or damageand accurately after loss or damage

Recovery facilities:Recovery facilities:• Backup FacilitiesBackup Facilities• Journalizing FacilitiesJournalizing Facilities• Checkpoint FacilityCheckpoint Facility• Recovery ManagerRecovery Manager

Chapter 13 2626

Back-up FacilitiesBack-up Facilities

• Automatic dump facility that produces Automatic dump facility that produces backup copy of the entire databasebackup copy of the entire database

• Periodic backup (e.g. nightly, weekly)Periodic backup (e.g. nightly, weekly)• Cold backup–database is shut down during Cold backup–database is shut down during

backupbackup• Hot backup–selected portion is shut down Hot backup–selected portion is shut down

and backed up at a given timeand backed up at a given time• Backups stored in secure, off-site locationBackups stored in secure, off-site location

Chapter 13 2727

Journalizing FacilitiesJournalizing Facilities• Audit trail of transactions and database Audit trail of transactions and database

updatesupdates• Transaction log–record of essential data for Transaction log–record of essential data for

each transaction processed against the each transaction processed against the databasedatabase

• Database change log–images of updated Database change log–images of updated datadata– Before-image–copy before modificationBefore-image–copy before modification– After-image–copy after modificationAfter-image–copy after modification

Produces an audit trailaudit trail

Chapter 13 2828

Figure 13-9 Database audit trail

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

Chapter 13 2929

Checkpoint FacilitiesCheckpoint Facilities

• DBMS periodically refuses to accept new DBMS periodically refuses to accept new transactionstransactions

• system is in a system is in a quietquiet state state• Database and transaction logs are Database and transaction logs are

synchronizedsynchronized

This allows recovery manager to resume processing from short period, instead of repeating entire day

Chapter 13 3030

Recovery and Restart ProceduresRecovery and Restart Procedures

• Disk Mirroring–switch between identical copies of Disk Mirroring–switch between identical copies of databasesdatabases

• Restore/Rerun–reprocess transactions against the Restore/Rerun–reprocess transactions against the backupbackup

• Transaction Integrity–commit or abort all Transaction Integrity–commit or abort all transaction changestransaction changes

• Backward Recovery (Rollback)–apply before Backward Recovery (Rollback)–apply before imagesimages

• Forward Recovery (Roll Forward)–apply after Forward Recovery (Roll Forward)–apply after images (preferable to restore/rerun)images (preferable to restore/rerun)

Chapter 13 3131

Transaction ACID PropertiesTransaction ACID Properties• AtomicAtomic

– Transaction cannot be subdividedTransaction cannot be subdivided• ConsistentConsistent

– Constraints don’t change from before transaction to after Constraints don’t change from before transaction to after transactiontransaction

• IsolatedIsolated– Database changes not revealed to users until after Database changes not revealed to users until after

transaction has completedtransaction has completed• DurableDurable

– Database changes are permanentDatabase changes are permanent

Chapter 13 3232

Figure 13-10 Basic recovery techniques a) Rollback

Chapter 13 3333

Figure 13-10 Basic recovery techniques (cont.)b) Rollforward

Chapter 13 3434

Database Failure ResponsesDatabase Failure Responses• Aborted transactionsAborted transactions

– Preferred recovery: rollbackPreferred recovery: rollback– Alternative: Rollforward to state just prior to abortAlternative: Rollforward to state just prior to abort

• Incorrect dataIncorrect data– Preferred recovery: rollbackPreferred recovery: rollback– Alternative 1: rerun transactions not including inaccurate data updatesAlternative 1: rerun transactions not including inaccurate data updates– Alternative 2: compensating transactionsAlternative 2: compensating transactions

• System failure (database intact)System failure (database intact)– Preferred recovery: switch to duplicate databasePreferred recovery: switch to duplicate database– Alternative 1: rollbackAlternative 1: rollback– Alternative 2: restart from checkpointAlternative 2: restart from checkpoint

• Database destructionDatabase destruction– Preferred recovery: switch to duplicate databasePreferred recovery: switch to duplicate database– Alternative 1: rollforwardAlternative 1: rollforward– Alternative 2: reprocess transactionsAlternative 2: reprocess transactions

Chapter 13 3535

Concurrency ControlConcurrency Control

• ProblemProblem–in a multi-user environment, –in a multi-user environment, simultaneous access to data can result in simultaneous access to data can result in interference and data lossinterference and data loss

• SolutionSolution––Concurrency ControlConcurrency Control– The process of managing simultaneous The process of managing simultaneous

operations against a database so that data operations against a database so that data integrity is maintained and the operations do integrity is maintained and the operations do not interfere with each other in a multi-user not interfere with each other in a multi-user environmentenvironment

Chapter 13 3636

Figure 13-11 Lost update (no concurrency control in effect)

Simultaneous access causes updates to cancel each otherA similar problem is the inconsistent readinconsistent read problem

Chapter 13 3737

Concurrency Control TechniquesConcurrency Control Techniques

• SerializabilitySerializability– Finish one transaction before starting anotherFinish one transaction before starting another

• Locking Mechanisms Locking Mechanisms – The most common way of achieving The most common way of achieving

serializationserialization– Data that is retrieved for the purpose of Data that is retrieved for the purpose of

updating is locked for the updaterupdating is locked for the updater– No other user can perform update until No other user can perform update until

unlockedunlocked

Chapter 13 3838

Figure 13-12: Updates with locking (concurrency control)

This prevents the lost update problem

Chapter 13 3939

Locking MechanismsLocking Mechanisms• Locking level:Locking level:

– Database–used during database updatesDatabase–used during database updates– Table–used for bulk updatesTable–used for bulk updates– Block or page–very commonly usedBlock or page–very commonly used– Record–only requested row; fairly commonly usedRecord–only requested row; fairly commonly used– Field–requires significant overhead; impracticalField–requires significant overhead; impractical

• Types of locks:Types of locks:– Shared lock–Read but no update permitted. Used Shared lock–Read but no update permitted. Used

when just reading to prevent another user from when just reading to prevent another user from placing an exclusive lock on the recordplacing an exclusive lock on the record

– Exclusive lock–No access permitted. Used when Exclusive lock–No access permitted. Used when preparing to updatepreparing to update

Chapter 13 4040

DeadlockDeadlock• An impasse that results when two or more transactions An impasse that results when two or more transactions

have locked common resources, and each waits for the have locked common resources, and each waits for the other to unlock their resourcesother to unlock their resources

Figure 13-13The problem of deadlock

John and Marsha will wait John and Marsha will wait forever for each other to forever for each other to release their locked release their locked resources!resources!

Chapter 13 4141

Managing DeadlockManaging Deadlock• Deadlock prevention:Deadlock prevention:

– Lock all records required at the beginning of a transactionLock all records required at the beginning of a transaction– Two-phase locking protocolTwo-phase locking protocol

• Growing phaseGrowing phase• Shrinking phaseShrinking phase

– May be difficult to determine all needed resources in May be difficult to determine all needed resources in advanceadvance

• Deadlock Resolution:Deadlock Resolution:– Allow deadlocks to occurAllow deadlocks to occur– Mechanisms for detecting and breaking themMechanisms for detecting and breaking them

• Resource usage matrixResource usage matrix

Chapter 13 4242

VersioningVersioning

• Optimistic approach to concurrency controlOptimistic approach to concurrency control• Instead of lockingInstead of locking• Assumption is that simultaneous updates will be Assumption is that simultaneous updates will be

infrequentinfrequent• Each transaction can attempt an update as it Each transaction can attempt an update as it

wisheswishes• The system will reject an update when it senses a The system will reject an update when it senses a

conflictconflict• Use of rollback and commit for thisUse of rollback and commit for this

Chapter 13 4343

Figure 13-15 The use of versioning

Better performance than locking

Chapter 13 4444

Data Dictionaries and RepositoriesData Dictionaries and Repositories• Data dictionaryData dictionary

– Documents data elements of a databaseDocuments data elements of a database

• System catalogSystem catalog– System-created database that describes all database objectsSystem-created database that describes all database objects

• Information RepositoryInformation Repository– Stores metadata describing data and data processing Stores metadata describing data and data processing

resourcesresources

• Information Repository Dictionary System (IRDS)Information Repository Dictionary System (IRDS)– Software tool managing/controlling access to information Software tool managing/controlling access to information

repositoryrepository

Chapter 13 4545

Figure 13-16 Three components of the repository system architecture

A schema of the repository information

Software that manages the repository objects

Where repository objects are stored

Source: adapted from Bernstein, 1996.

Chapter 13 4646

Database Performance TuningDatabase Performance Tuning• DBMS InstallationDBMS Installation

– Setting installation parametersSetting installation parameters• Memory Usage Memory Usage

– Set cache levelsSet cache levels– Choose background processesChoose background processes

• Input/Output (I/O) ContentionInput/Output (I/O) Contention– Use stripingUse striping– Distribution of heavily accessed filesDistribution of heavily accessed files

• CPU UsageCPU Usage– Monitor CPU loadMonitor CPU load

• Application tuningApplication tuning– Modification of SQL code in applicationsModification of SQL code in applications

Chapter 13 4747

Data AvailabilityData Availability

• Downtime is expensiveDowntime is expensive• How to ensure availabilityHow to ensure availability

– Hardware failures–provide redundancy for fault Hardware failures–provide redundancy for fault tolerancetolerance

– Loss of data–database mirroringLoss of data–database mirroring– Maintenance downtime–automated and non-Maintenance downtime–automated and non-

disruptive maintenance utilitiesdisruptive maintenance utilities– Network problems–careful traffic monitoring, Network problems–careful traffic monitoring,

firewalls, and routersfirewalls, and routers

Chapter 13 4848

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