Chapter 12Chapter 12Database Control Issues: Database Control Issues:

Security, Backup and Recovery, Security, Backup and Recovery, ConcurrencyConcurrency

Fundamentals of Database Management Systemsby

Mark L. Gillenson, Ph.D.

University of Memphis

Presentation by: Amita Goyal Chin, Ph.D.

Virginia Commonwealth University

John Wiley & Sons, Inc.

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Chapter ObjectivesChapter Objectives

List the major data control issues handled List the major data control issues handled by database management systems. by database management systems.

List and describe the types of data security List and describe the types of data security breaches. breaches.

List and describe the types of data security List and describe the types of data security measures. measures.

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Chapter ObjectivesChapter Objectives

Describe the concept of backup and Describe the concept of backup and recovery. recovery.

Describe the major backup and recovery Describe the major backup and recovery techniques. techniques.

Explain the problem of disaster recovery. Explain the problem of disaster recovery.

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Chapter ObjectivesChapter Objectives

Describe the concept of concurrency Describe the concept of concurrency control. control.

Describe such concurrency control issues Describe such concurrency control issues and measures as the lost update problem, and measures as the lost update problem, locks and deadlock, and versioning. locks and deadlock, and versioning.

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Database Control IssuesDatabase Control Issues Different corporate resources have different Different corporate resources have different

management requirements.management requirements. Money must be protected from theftMoney must be protected from theft Equipment must be secured against misuseEquipment must be secured against misuse Buildings may require security guardsBuildings may require security guards

Data is a corporate resource and has its own peculiar Data is a corporate resource and has its own peculiar concerns, which we call database control issues.concerns, which we call database control issues. Data securityData security Backup and recoveryBackup and recovery Concurrency controlConcurrency control

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Database Control IssuesDatabase Control Issues

Data Security - protecting the data from theft, Data Security - protecting the data from theft, from malicious destruction, from unauthorized from malicious destruction, from unauthorized updating, etc.updating, etc.

Backup and Recovery - having procedures in Backup and Recovery - having procedures in place to recreate data that has been lost, for any place to recreate data that has been lost, for any reason.reason.

Concurrency Control - problems that can occur Concurrency Control - problems that can occur when two or more transactions or users attempt when two or more transactions or users attempt to update a piece of data simultaneously.to update a piece of data simultaneously.

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The Importance of Data The Importance of Data SecuritySecurity

Good data security is absolutely critical to every Good data security is absolutely critical to every company and organization.company and organization.

A data security breach can dramatically affect a A data security breach can dramatically affect a company’s ability to continue normal functioning.company’s ability to continue normal functioning.

Customer data, which, for example, can be Customer data, which, for example, can be financial, medical, or legal in nature, must be financial, medical, or legal in nature, must be carefully guarded.carefully guarded.

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Types of Data Security Types of Data Security BreachesBreaches

Unauthorized Data Access - someone obtains Unauthorized Data Access - someone obtains data that she is not authorized to see.data that she is not authorized to see.

Unauthorized Data or Program Modification - Unauthorized Data or Program Modification - someone changes the value of stored data that someone changes the value of stored data that they are not entitled to change.they are not entitled to change.

Malicious Mischief - someone can corrupt or Malicious Mischief - someone can corrupt or even erase some of a company’s data; hardware even erase some of a company’s data; hardware can be damaged, making data unusable.can be damaged, making data unusable.

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Methods of Breaching Data Methods of Breaching Data SecuritySecurity

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Methods of Breaching Data Methods of Breaching Data SecuritySecurity

Unauthorized Computer AccessUnauthorized Computer Access Intercepting Data CommunicationsIntercepting Data Communications Stealing Disks or ComputersStealing Disks or Computers Computer VirusesComputer Viruses Damaging Computer HardwareDamaging Computer Hardware

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Unauthorized Computer Unauthorized Computer AccessAccess

By “hacking” or gaining access from outside of By “hacking” or gaining access from outside of the company.the company. Some hackers are software experts.Some hackers are software experts. Some hackers have stolen identification names and Some hackers have stolen identification names and

passwords and can enter a computer looking like passwords and can enter a computer looking like legitimate users.legitimate users.

Legitimate users, e.g., employees stealing dataLegitimate users, e.g., employees stealing data

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Intercepting Data Intercepting Data CommunicationsCommunications

““Wiretapping”Wiretapping”

Data can be stolen while it is being transmitted.Data can be stolen while it is being transmitted.

Twisted-pair telephone wire or coaxial cable can be Twisted-pair telephone wire or coaxial cable can be tapped.tapped.

Data bounced off satellites may be intercepted.Data bounced off satellites may be intercepted.

Light pulses with fiber-optic transmission cannot be Light pulses with fiber-optic transmission cannot be easily tapped.easily tapped.

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Stealing Disks or ComputersStealing Disks or Computers

Zip Disks, 3.5” diskettes, and CDs all have Zip Disks, 3.5” diskettes, and CDs all have the potential of being stolen.the potential of being stolen.

Laptop computers can be stolen.Laptop computers can be stolen.

Even desktop computers have been stolen Even desktop computers have been stolen from company offices.from company offices.

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Computer VirusesComputer Viruses

A malicious piece of software that is A malicious piece of software that is capable of copying itself and “spreading” capable of copying itself and “spreading” from computer to computer on diskettes from computer to computer on diskettes and through telecommunications lines.and through telecommunications lines.

Computer viruses that travel along data Computer viruses that travel along data communications lines are also called communications lines are also called wormsworms..

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Damaging Computer Damaging Computer HardwareHardware

Might be either deliberate or accidental.Might be either deliberate or accidental. FiresFires Coffee spillsCoffee spills HurricanesHurricanes Disgruntled or newly fired employees with Disgruntled or newly fired employees with

hammers or whatever other hard objects were hammers or whatever other hard objects were handy.handy.

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Types of Data Security Types of Data Security MeasuresMeasures

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Physical Security of Company Physical Security of Company PremisesPremises

Don’t put the computer in the basement Don’t put the computer in the basement because of the possibility of floods.because of the possibility of floods.

Don’t put the computer on the ground floor Don’t put the computer on the ground floor because of the possibility of a truck driving because of the possibility of a truck driving into the building, accidentally or on into the building, accidentally or on purpose.purpose.

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Physical Security of Company Physical Security of Company PremisesPremises

Don’t put the computer above the eighth Don’t put the computer above the eighth floor because that’s as high as fire truck floor because that’s as high as fire truck ladders can reach.ladders can reach.

Don’t put the computer on the top floor of Don’t put the computer on the top floor of the building because it is subject to the building because it is subject to helicopter landing and attack. helicopter landing and attack.

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Physical Security of Company Physical Security of Company PremisesPremises

If you occupy at least three floors of the If you occupy at least three floors of the building, don’t put the computer on your building, don’t put the computer on your topmost floor because its ceiling is another topmost floor because its ceiling is another company’s floor, and don’t put the company’s floor, and don’t put the computer on your bottommost floor computer on your bottommost floor because its floor is another company’s because its floor is another company’s ceiling.ceiling.

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Physical Security of Company Physical Security of Company PremisesPremises

Whatever floor you put the computer on, Whatever floor you put the computer on, keep it in an interior space away from the keep it in an interior space away from the windows.windows.

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Physical Security: Limit Physical Security: Limit AccessAccess

Access should be limited to those people Access should be limited to those people who have a legitimate need to be in the who have a legitimate need to be in the computer room.computer room.

Control access to the room.Control access to the room.

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Physical Security: Access to Physical Security: Access to RoomRoom

Require something people know, such as a secret code Require something people know, such as a secret code to be punched in.to be punched in.

Require people have something, such as a magnetic Require people have something, such as a magnetic stripe card, possibly combined with a secret code.stripe card, possibly combined with a secret code.

Use some human part that can be measured or Use some human part that can be measured or scanned. These biometric systems can be based on scanned. These biometric systems can be based on fingerprints, the dimensions and positions of facial fingerprints, the dimensions and positions of facial features, retinal blood vessel patterns, or voice patterns. features, retinal blood vessel patterns, or voice patterns.

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Controlled Access to the Controlled Access to the Computer SystemComputer System

First line of defense:First line of defense: Identification tagIdentification tag PasswordPassword

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PasswordPassword

Must be kept secret.Must be kept secret.

Must be changed periodically.Must be changed periodically.

Must not be written down.Must not be written down.

Should not appear on the terminal screen when Should not appear on the terminal screen when typed.typed.

Should be user-created.Should be user-created.

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Access to the DatabaseAccess to the Database

Restrict access to specific data so that only Restrict access to specific data so that only specific people can retrieve or modify it.specific people can retrieve or modify it.

Some systems have such controls in the Some systems have such controls in the operating system or in other utility software.operating system or in other utility software.

An additional layer of passwords may also be An additional layer of passwords may also be introduced.introduced.

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Access to the DatabaseAccess to the Database

At the DBMS level a user cannot simply At the DBMS level a user cannot simply access any data he wants to; users have access any data he wants to; users have to be given explicit authorization to access to be given explicit authorization to access data.data.

Use views (CREATE VIEW)Use views (CREATE VIEW)

Use SQL GRANT command.Use SQL GRANT command.

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Data EncryptionData Encryption

Data is changed, bit-by-bit or character-by-Data is changed, bit-by-bit or character-by-character, into a form that looks totally character, into a form that looks totally garbled.garbled.

Data can be stored, transmitted, etc. Data can be stored, transmitted, etc. encrypted.encrypted.

To be used, data must be decrypted.To be used, data must be decrypted.

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Data EncryptionData Encryption

Encryption generally involves a data Encryption generally involves a data conversion algorithm and a secret key.conversion algorithm and a secret key.

The recipient must be aware of both the The recipient must be aware of both the algorithm and the secret key so that it can algorithm and the secret key so that it can work the algorithm in reverse and decrypt work the algorithm in reverse and decrypt the data.the data.

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Data Encryption TechniquesData Encryption Techniques

Symmetric or private key encryptionSymmetric or private key encryption

Asymmetric or public key encryptionAsymmetric or public key encryption

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Symmetric EncryptionSymmetric Encryption

Require the same long bit-by-bit key for Require the same long bit-by-bit key for encrypting and decrypting the data.encrypting and decrypting the data.

Transmitting the private key may Transmitting the private key may compromise the key.compromise the key.

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Asymmetric EncryptionAsymmetric Encryption

Uses two different keys:Uses two different keys: Public key - used for encrypting the dataPublic key - used for encrypting the data Private key - used for decrypting the dataPrivate key - used for decrypting the data

Process tends to be slower than Process tends to be slower than symmetric encryption.symmetric encryption.

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SSL TechnologySSL Technology

Secure Socket LayerSecure Socket Layer

A combination of private key and public A combination of private key and public key encryption.key encryption.

Used on the World Wide Web.Used on the World Wide Web.

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SSL - Usage ExampleSSL - Usage Example

A person at home who wants to buy A person at home who wants to buy something from an online store.something from an online store.

Her PC and its WWW browser are the Her PC and its WWW browser are the client.client.

The online store’s computer is the server.The online store’s computer is the server.

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SSL - Usage ExampleSSL - Usage Example

Both sides want to conduct the secure Both sides want to conduct the secure transaction using private key technology.transaction using private key technology.

They have the problem of one side picking They have the problem of one side picking a private key and getting it to the other a private key and getting it to the other side in a secure manner.side in a secure manner.

How do they do it?How do they do it?

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SSL - Usage ExampleSSL - Usage Example

The client contacts the serverThe client contacts the server

The server sends the client its public key for its The server sends the client its public key for its public key algorithm.public key algorithm. No one cares if this public key is stolen.No one cares if this public key is stolen.

The client, using a random number generator, The client, using a random number generator, creates a “session key.”creates a “session key.” the key for the private key algorithm with which the the key for the private key algorithm with which the

secure transaction will be conductedsecure transaction will be conducted

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SSL - Usage ExampleSSL - Usage Example

The problemThe problem: How is the client going to : How is the client going to securely transmit the session key it securely transmit the session key it generated to the server, since both must generated to the server, since both must have it to use the private key algorithm for have it to use the private key algorithm for the transaction? the transaction?

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SSL - Usage ExampleSSL - Usage Example

The client is going to send the session key The client is going to send the session key to the server securely, using a public key to the server securely, using a public key algorithm and the server’s public key.algorithm and the server’s public key. The client encrypts the session key using the The client encrypts the session key using the

server’s public keyserver’s public key

The client transmits the encrypted session The client transmits the encrypted session key to the server with the public key key to the server with the public key algorithm.algorithm.

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SSL - Usage ExampleSSL - Usage Example

Once the session key has been securely Once the session key has been securely transmitted to the server, both the client transmitted to the server, both the client and the server have it and the secure and the server have it and the secure transaction can proceed using the private transaction can proceed using the private key algorithm.key algorithm.

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Antivirus SoftwareAntivirus Software

Used to combat computer viruses.Used to combat computer viruses.

Two basic methods:Two basic methods: Virus signatures - portions of the virus code Virus signatures - portions of the virus code

that are considered to be unique to it.that are considered to be unique to it.

Monitoring - software constantly monitors the Monitoring - software constantly monitors the computer environment to watch for requests computer environment to watch for requests or commands for any unusual activity.or commands for any unusual activity.

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FirewallsFirewalls

Software or a combination of hardware Software or a combination of hardware and software that protects a company’s and software that protects a company’s computer and its data against external computer and its data against external attack via data communications lines.attack via data communications lines.

Different kinds of firewalls.Different kinds of firewalls.

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Firewall: Proxy ServerFirewall: Proxy Server

A firewall that is a combination of hardware and software.A firewall that is a combination of hardware and software.

The proxy server takes apart the incoming message, extracts the The proxy server takes apart the incoming message, extracts the legitimate pieces of data, reformats the data for the company’s legitimate pieces of data, reformats the data for the company’s mainframe, and passes the data on to the company’s main mainframe, and passes the data on to the company’s main computer.computer.

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Training Employees in Good Training Employees in Good Security PracticesSecurity Practices

Log off your computer or at least lock your Log off your computer or at least lock your office door when you leave your office.office door when you leave your office.

Don’t write your computer password down Don’t write your computer password down anywhere.anywhere.

Don’t respond to any unusual requests for Don’t respond to any unusual requests for information about the computer system information about the computer system from anyone over the telephone. from anyone over the telephone.

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Training Employees in Good Training Employees in Good Security PracticesSecurity Practices

Don’t leave diskettes or other storage Don’t leave diskettes or other storage media lying around your office.media lying around your office.

Don’t take diskettes or other storage Don’t take diskettes or other storage media out of the building.media out of the building.

Don’t assume that a stranger in the Don’t assume that a stranger in the building is there legitimately without building is there legitimately without checking.checking.

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Backup and RecoveryBackup and Recovery

We have to assume that from time to time We have to assume that from time to time something will go wrong with our data, and something will go wrong with our data, and so we have to have the tools available to so we have to have the tools available to correct or reconstruct it.correct or reconstruct it.

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Backup Copies and JournalsBackup Copies and Journals

Two basic but very important tasks:Two basic but very important tasks: backing up the databasebacking up the database maintaining a journalmaintaining a journal

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BackupBackup

On a regularly scheduled basis, a On a regularly scheduled basis, a company’s databases must be backed up company’s databases must be backed up or copied.or copied.

The backup copy must be put in a safe The backup copy must be put in a safe place, away from the original in the place, away from the original in the computer system.computer system.

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Maintaining a JournalMaintaining a Journal

Tracks all changes that take place in the Tracks all changes that take place in the data.data. Updates to existing recordsUpdates to existing records Insertion of new recordsInsertion of new records Deletion of existing recordsDeletion of existing records

Does not track Does not track readread operations, because operations, because they do not change the data.they do not change the data.

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Database LogDatabase Log

Started immediately after the data is backup up.Started immediately after the data is backup up.

Two types:Two types: Change log / before and after image logChange log / before and after image log

• Records data value before and after a changeRecords data value before and after a change

Transaction logTransaction log• Keeps a record of the program that changed the data and all Keeps a record of the program that changed the data and all

of the inputs that the program used.of the inputs that the program used.

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(Roll) Forward Recovery(Roll) Forward Recovery

Assume a database table has been lost.Assume a database table has been lost.

To recreate this table:To recreate this table: Ready the last backup copy of the table.Ready the last backup copy of the table. Ready the logReady the log Roll forward in the log, applying the changes Roll forward in the log, applying the changes

that were made to the table since the last that were made to the table since the last backup.backup.

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Forward RecoveryForward Recovery

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Change LogChange Log

Only the last one of the changes to the Only the last one of the changes to the particular piece of data, which shows the particular piece of data, which shows the value of this piece of data at the point that value of this piece of data at the point that the table was destroyed, needs to be used the table was destroyed, needs to be used in updating the database copy in the roll-in updating the database copy in the roll-forward operation.forward operation.

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Backward Recovery or Backward Recovery or RollbackRollback

Suppose that in the midst of normal Suppose that in the midst of normal operation an error is discovered that operation an error is discovered that involves a piece of recently updated data.involves a piece of recently updated data.

The discovered error, and all other The discovered error, and all other changes that were made to the database changes that were made to the database since the error was discovered, must be since the error was discovered, must be backed out.backed out.

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Backward RecoveryBackward Recovery

Start with the Start with the database in its current database in its current state.state.

The log is positioned The log is positioned at the last entry.at the last entry.

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Backward RecoveryBackward Recovery

A recovery program A recovery program proceeds backwards proceeds backwards through the log, through the log, resetting each resetting each updated data value in updated data value in the database to its the database to its “before image,” until it “before image,” until it reaches the point reaches the point where the error was where the error was made.made.

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Duplicate or Mirrored Duplicate or Mirrored DatabasesDatabases

Two copies of the Two copies of the entire database are entire database are maintained, and both maintained, and both are updated are updated simultaneously.simultaneously.

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Duplicate or Mirrored Duplicate or Mirrored DatabasesDatabases

Advantage: If one system Advantage: If one system is destroyed, the is destroyed, the applications that use the applications that use the database can just keep database can just keep on running with the on running with the duplicate database.duplicate database.

Disadvantage: This is a Disadvantage: This is a relatively expensive relatively expensive proposition.proposition.

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Disaster RecoveryDisaster Recovery

Rebuilding an entire information system or Rebuilding an entire information system or significant parts of one, after a significant parts of one, after a catastrophic natural disaster such as:catastrophic natural disaster such as: a hurricanea hurricane a tornadoa tornado a earthquakea earthquake a building collapsea building collapse a major firea major fire

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Being Prepared for Disaster Being Prepared for Disaster RecoveryRecovery

Maintain totally mirrored systems (not just Maintain totally mirrored systems (not just databases) in different cities.databases) in different cities.

Contract with a company that maintains Contract with a company that maintains hardware similar to yours (a hot site) so that you hardware similar to yours (a hot site) so that you can be up and running again quickly after a can be up and running again quickly after a disaster.disaster.

Build a computer center that is relatively disaster Build a computer center that is relatively disaster proof.proof.

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Being Prepared for Disaster Being Prepared for Disaster RecoveryRecovery

Maintain space (a cold site) with electrical Maintain space (a cold site) with electrical connections, air conditioning, etc., into connections, air conditioning, etc., into which new hardware can be moved if need which new hardware can be moved if need be.be.

Make a reciprocal arrangement with Make a reciprocal arrangement with another company with hardware similar to another company with hardware similar to yours to aid each other in case one suffers yours to aid each other in case one suffers a disaster.a disaster.

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Concurrency ControlConcurrency Control

Many people using today’s applications Many people using today’s applications systems will require access to the same systems will require access to the same data at the same time.data at the same time.

Two or more users attempting to update Two or more users attempting to update some data simultaneously will conflict.some data simultaneously will conflict.

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The Lost Update ProblemThe Lost Update Problem

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Locks and DeadlockLocks and Deadlock

When a user begins an update operation When a user begins an update operation on a piece of data, the DBMS locks that on a piece of data, the DBMS locks that data. data.

Any attempt to begin another update Any attempt to begin another update operation on that same piece of data will operation on that same piece of data will be blocked, or “locked out,” until the first be blocked, or “locked out,” until the first update operation is completed and its lock update operation is completed and its lock on the data is released.on the data is released.

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LocksLocks

Prevents the Lost Update Problem.Prevents the Lost Update Problem.

Granularity of lock can vary.Granularity of lock can vary. Entire tableEntire table Record levelRecord level Etc.Etc.

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DeadlockDeadlock

Two or more transactions must each Two or more transactions must each update the same, multiple pieces of data.update the same, multiple pieces of data.

They each wait endlessly for the other to They each wait endlessly for the other to release the data that each has already release the data that each has already locked.locked.

Also called the deadly embrace.Also called the deadly embrace.

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DeadlockDeadlock

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Handling DeadlockHandling Deadlock

Deadlock PreventionDeadlock Prevention Difficult to accomplishDifficult to accomplish

Deadlock DetectionDeadlock Detection Allow deadlock to occurAllow deadlock to occur Detect occurrenceDetect occurrence Abort one of the deadlocked transactionsAbort one of the deadlocked transactions

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VersioningVersioning

Does not involve locks at all.Does not involve locks at all.

Each transaction is given a copy or “version” of Each transaction is given a copy or “version” of the data that it needs for an update operation.the data that it needs for an update operation.

Each transaction records its result in its own Each transaction records its result in its own copy of the data.copy of the data.

Then each transaction tries to update the actual Then each transaction tries to update the actual database with its result.database with its result.

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VersioningVersioning

Monitoring software checks to see if there Monitoring software checks to see if there is a conflict between two or more is a conflict between two or more transactions trying to update the same transactions trying to update the same data at the same time.data at the same time.

If there is, the software allows one of the If there is, the software allows one of the transactions to update the database and transactions to update the database and makes the other(s) start over again. makes the other(s) start over again.

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