1. © 2007 by Prentice Hall 1 Chapter 12: Data and Database Administration Modern Database Management 8 th Edition Jeffrey A. Hoffer, Mary B. Prescott, Fred R. McFadden

2. Chapter 12 © 2007 by Prentice Hall 2 Objectives Definition of terms Definition of terms List functions and roles of data/database administration List functions and roles of data/database administration Describe role of data dictionaries and information repositories Describe role of data dictionaries and information repositories Compare optimistic and pessimistic concurrency control Compare optimistic and pessimistic concurrency control Describe problems and techniques for data security Describe problems and techniques for data security Describe problems and techniques for data recovery Describe problems and techniques for data recovery Describe database tuning issues and list areas where changes can be done to tune the database Describe database tuning issues and list areas where changes can be done to tune the database Describe importance and measures of data quality Describe importance and measures of data quality Describe importance and measures of data availability Describe importance and measures of data availability

3. Chapter 12 © 2007 by Prentice Hall 3 Traditional Administration 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 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 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

4. Chapter 12 © 2007 by Prentice Hall 4 Traditional Data Administration Functions Data policies, procedures, standards Data policies, procedures, standards Planning Planning Data conflict (ownership) resolution Data conflict (ownership) resolution Managing the information repository Managing the information repository Internal marketing of DA concepts Internal marketing of DA concepts

5. Chapter 12 © 2007 by Prentice Hall 5 Traditional Database Administration Functions Selection of DBMS and software tools Selection of DBMS and software tools Installing/upgrading DBMS Installing/upgrading DBMS Tuning database performance Tuning database performance Improving query processing performance Improving query processing performance Managing data security, privacy, and integrity Managing data security, privacy, and integrity Data backup and recovery Data backup and recovery

6. Chapter 12 © 2007 by Prentice Hall 6 Evolving Approaches to Data Administration Blend data and database administration into one role Blend data and database administration into one role Fast-track development – monitoring development process (analysis, design, implementation, maintenance) Fast-track development – monitoring development process (analysis, design, implementation, maintenance) Procedural DBAs–managing quality of triggers and stored procedures Procedural DBAs–managing quality of triggers and stored procedures eDBA–managing Internet-enabled database applications eDBA–managing Internet-enabled database applications PDA DBA–data synchronization and personal database management PDA DBA–data synchronization and personal database management Data warehouse administration Data warehouse administration

7. Chapter 12 © 2007 by Prentice Hall 7 Data Warehouse Administration New role, coming with the growth in data warehouses New role, coming with the growth in data warehouses Similar to DA/DBA roles Similar to DA/DBA roles Emphasis on integration and coordination of metadata/data across many data sources Emphasis on integration and coordination of metadata/data across many data sources Specific roles: Specific roles: Support DSS applications Support DSS applications Manage data warehouse growth Manage data warehouse growth Establish service level agreements regarding data warehouses and data marts Establish service level agreements regarding data warehouses and data marts

8. Chapter 12 © 2007 by Prentice Hall 8 Open Source DBMSs An alternative to proprietary packages such as Oracle, Microsoft SQL Server, or Microsoft Access An alternative to proprietary packages such as Oracle, Microsoft SQL Server, or Microsoft Access mySQL is an example of open-source DBMS mySQL is an example of open-source DBMS Less expensive than proprietary packages Less expensive than proprietary packages Source code available, for modification Source code available, for modification

9. Chapter 12 © 2007 by Prentice Hall 9 Figure 12-2 Data modeling responsibilities

10. Chapter 12 © 2007 by Prentice Hall 10 Database Security Database Security: Protection of the data against accidental or intentional loss, destruction, or misuse Database Security: Protection of the data against accidental or intentional loss, destruction, or misuse Increased difficulty due to Internet access and client/server technologies Increased difficulty due to Internet access and client/server technologies

11. Chapter 12 © 2007 by Prentice Hall 11 Figure 12-3 Possible locations of data security threats

12. Chapter 12 © 2007 by Prentice Hall 12 Threats to Data Security Accidental losses attributable to: Accidental losses attributable to: Human error Human error Software failure Software failure Hardware failure Hardware failure Theft and fraud Theft 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 integrity Loss of data integrity Loss of availability (through, e.g. sabotage) Loss of availability (through, e.g. sabotage)

13. Chapter 12 © 2007 by Prentice Hall 13 Figure 12-4 Establishing Internet Security

14. Chapter 12 © 2007 by Prentice Hall 14 Web Security Static HTML files are easy to secure Static HTML files are easy to secure Standard database access controls Standard database access controls Place Web files in protected directories on server Place Web files in protected directories on server Dynamic pages are harder Dynamic pages are harder Control of CGI scripts Control of CGI scripts User authentication User authentication Session security Session security SSL for encryption SSL for encryption Restrict number of users and open ports Restrict number of users and open ports Remove unnecessary programs Remove unnecessary programs

15. Chapter 12 © 2007 by Prentice Hall 15 W3C Web Privacy Standard Platform for Privacy Protection (P3P) Platform for Privacy Protection (P3P) Addresses the following: Addresses the following: Who collects data Who collects data What data is collected and for what purpose What data is collected and for what purpose Who is data shared with Who is data shared with Can users control access to their data Can users control access to their data How are disputes resolved How are disputes resolved Policies for retaining data Policies for retaining data Where are policies kept and how can they be accessed Where are policies kept and how can they be accessed

16. Chapter 12 © 2007 by Prentice Hall 16 Database Software Security Features Views or subschemas Views or subschemas Integrity controls Integrity controls Authorization rules Authorization rules User-defined procedures User-defined procedures Encryption Encryption Authentication schemes Authentication schemes Backup, journalizing, and checkpointing Backup, journalizing, and checkpointing

17. Chapter 12 © 2007 by Prentice Hall 17 Views and Integrity Controls Views Views Subset of the database that is presented to one or more users 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 User can be given access privilege to view without allowing access privilege to underlying tables Integrity Controls Integrity Controls Protect data from unauthorized use Protect data from unauthorized use Domains–set allowable values Domains–set allowable values Assertions–enforce database conditions Assertions–enforce database conditions

18. Chapter 12 © 2007 by Prentice Hall 18 Authorization Rules Controls incorporated in the data management system Controls incorporated in the data management system  Restrict:  Restrict: access to data access to data actions that people can take on data actions that people can take on data  Authorization matrix for:  Authorization matrix for: Subjects Subjects Objects Objects Actions Actions Constraints Constraints

19. Chapter 12 © 2007 by Prentice Hall 19 Figure 12-5 Authorization matrix

20. Chapter 12 © 2007 by Prentice Hall 20 Some DBMSs also provide capabilities for user- defined procedures to customize the authorization process Figure 12-6a Authorization table for subjects (salespeople) Figure 12-6b Authorization table for objects (orders) Figure 12-7 Oracle privileges Implementing authorization rules

21. Chapter 12 © 2007 by Prentice Hall 21 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 12-8 Basic two-key encryption

22. Chapter 12 © 2007 by Prentice Hall 22 Authentication Schemes Goal – obtain a positive identification of the user Goal – obtain a positive identification of the user Passwords: First line of defense Passwords: First line of defense Should be at least 8 characters long Should be at least 8 characters long Should combine alphabetic and numeric data Should combine alphabetic and numeric data Should not be complete words or personal information Should not be complete words or personal information Should be changed frequently Should be changed frequently

23. Chapter 12 © 2007 by Prentice Hall 23 Authentication Schemes (cont.) Strong Authentication Strong Authentication Passwords are flawed: Passwords are flawed: Users share them with each other Users share them with each other They get written down, could be copied They get written down, could be copied Automatic logon scripts remove need to explicitly type them in Automatic logon scripts remove need to explicitly type them in Unencrypted passwords travel the Internet Unencrypted passwords travel the Internet Possible solutions: Possible solutions: Two factor–e.g. smart card plus PIN Two factor–e.g. smart card plus PIN Three factor–e.g. smart card, biometric, PIN Three factor–e.g. smart card, biometric, PIN Biometric devices–use of fingerprints, retinal scans, etc. for positive ID Biometric devices–use of fingerprints, retinal scans, etc. for positive ID Third-party mediated authentication–using secret keys, digital certificates Third-party mediated authentication–using secret keys, digital certificates

24. Chapter 12 © 2007 by Prentice Hall 24 Security Policies and Procedures Personnel controls Personnel controls Hiring practices, employee monitoring, security training Hiring practices, employee monitoring, security training Physical access controls Physical access controls Equipment locking, check-out procedures, screen placement Equipment locking, check-out procedures, screen placement Maintenance controls Maintenance controls Maintenance agreements, access to source code, quality and availability standards Maintenance agreements, access to source code, quality and availability standards Data privacy controls Data privacy controls Adherence to privacy legislation, access rules Adherence to privacy legislation, access rules

25. Chapter 12 © 2007 by Prentice Hall 25 Database Recovery  Mechanism for restoring a database quickly and accurately after loss or damage  Recovery facilities: Backup Facilities Backup Facilities Journalizing Facilities Journalizing Facilities Checkpoint Facility Checkpoint Facility Recovery Manager Recovery Manager

26. Chapter 12 © 2007 by Prentice Hall 26 Back-up Facilities Automatic dump facility that produces backup copy of the entire database Automatic dump facility that produces backup copy of the entire database Periodic backup (e.g. nightly, weekly) Periodic backup (e.g. nightly, weekly) Cold backup–database is shut down during backup Cold backup–database is shut down during backup Hot backup–selected portion is shut down and backed up at a given time Hot backup–selected portion is shut down and backed up at a given time Backups stored in secure, off-site location Backups stored in secure, off-site location

27. Chapter 12 © 2007 by Prentice Hall 27 Journalizing Facilities Audit trail of transactions and database updates Audit trail of transactions and database updates Transaction log–record of essential data for each transaction processed against the database Transaction log–record of essential data for each transaction processed against the database Database change log–images of updated data Database change log–images of updated data Before-image–copy before modification Before-image–copy before modification After-image–copy after modification After-image–copy after modification audit trail Produces an audit trail

28. Chapter 12 © 2007 by Prentice Hall 28 Figure 12-9 Database audit trail From the backup and logs, databases can be restored in case of damage or loss

29. Chapter 12 © 2007 by Prentice Hall 29 Checkpoint Facilities DBMS periodically refuses to accept new transactions DBMS periodically refuses to accept new transactions  system is in a quiet state  system is in a quiet state Database and transaction logs are synchronized Database and transaction logs are synchronized This allows recovery manager to resume processing from short period, instead of repeating entire day

30. Chapter 12 © 2007 by Prentice Hall 30 Recovery and Restart Procedures Disk Mirroring–switch between identical copies of databases Disk Mirroring–switch between identical copies of databases Restore/Rerun–reprocess transactions against the backup Restore/Rerun–reprocess transactions against the backup Transaction Integrity–commit or abort all transaction changes Transaction Integrity–commit or abort all transaction changes Backward Recovery (Rollback)–apply before images Backward Recovery (Rollback)–apply before images Forward Recovery (Roll Forward)–apply after images (preferable to restore/rerun) Forward Recovery (Roll Forward)–apply after images (preferable to restore/rerun)

31. Chapter 12 © 2007 by Prentice Hall 31 Transaction ACID Properties Atomic Atomic Transaction cannot be subdivided Transaction cannot be subdivided Consistent Consistent Constraints don’t change from before transaction to after transaction Constraints don’t change from before transaction to after transaction Isolated Isolated Database changes not revealed to users until after transaction has completed Database changes not revealed to users until after transaction has completed Durable Durable Database changes are permanent Database changes are permanent

32. Chapter 12 © 2007 by Prentice Hall 32 Figure 12-10 Basic recovery techniques a) Rollback

33. Chapter 12 © 2007 by Prentice Hall 33 Figure 12-10 Basic recovery techniques (cont.) b) Rollforward

34. Chapter 12 © 2007 by Prentice Hall 34 Database Failure Responses Aborted transactions Aborted transactions Preferred recovery: rollback Preferred recovery: rollback Alternative: Rollforward to state just prior to abort Alternative: Rollforward to state just prior to abort Incorrect data Incorrect data Preferred recovery: rollback Preferred recovery: rollback Alternative 1: rerun transactions not including inaccurate data updates Alternative 1: rerun transactions not including inaccurate data updates Alternative 2: compensating transactions Alternative 2: compensating transactions System failure (database intact) System failure (database intact) Preferred recovery: switch to duplicate database Preferred recovery: switch to duplicate database Alternative 1: rollback Alternative 1: rollback Alternative 2: restart from checkpoint Alternative 2: restart from checkpoint Database destruction Database destruction Preferred recovery: switch to duplicate database Preferred recovery: switch to duplicate database Alternative 1: rollforward Alternative 1: rollforward Alternative 2: reprocess transactions Alternative 2: reprocess transactions

35. Chapter 12 © 2007 by Prentice Hall 35 Concurrency Control Problem–in a multiuser environment, simultaneous access to data can result in interference and data loss Problem–in a multiuser environment, simultaneous access to data can result in interference and data loss Solution–Concurrency Control Solution–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 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

36. Chapter 12 © 2007 by Prentice Hall 36 Figure 12-11 Lost update (no concurrency control in effect) Simultaneous access causes updates to cancel each other inconsistent read A similar problem is the inconsistent read problem

37. Chapter 12 © 2007 by Prentice Hall 37 Concurrency Control Techniques Serializability Serializability Finish one transaction before starting another Finish one transaction before starting another Locking Mechanisms Locking Mechanisms The most common way of achieving serialization The most common way of achieving serialization Data that is retrieved for the purpose of updating is locked for the updater Data that is retrieved for the purpose of updating is locked for the updater No other user can perform update until unlocked No other user can perform update until unlocked

38. Chapter 12 © 2007 by Prentice Hall 38 Figure 12-12: Updates with locking (concurrency control) This prevents the lost update problem

39. Chapter 12 © 2007 by Prentice Hall 39 Locking Mechanisms Locking level: Locking level: Database–used during database updates Database–used during database updates Table–used for bulk updates Table–used for bulk updates Block or page–very commonly used Block or page–very commonly used Record–only requested row; fairly commonly used Record–only requested row; fairly commonly used Field–requires significant overhead; impractical Field–requires significant overhead; impractical Types of locks: Types of locks: Shared lock–Read but no update permitted. Used when just reading to prevent another user from placing an exclusive lock on the record Shared lock–Read but no 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 Exclusive lock–No access permitted. Used when preparing to update

40. Chapter 12 © 2007 by Prentice Hall 40 Deadlock An impasse that results when two or more transactions have locked common resources, and each waits for the other to unlock their resources An impasse that results when two or more transactions have locked common resources, and each waits for the other to unlock their resources Figure 12-13 The problem of deadlock John and Marsha will wait forever for each other to release their locked resources!

41. Chapter 12 © 2007 by Prentice Hall 41 Managing Deadlock Deadlock prevention: Deadlock prevention: Lock all records required at the beginning of a transaction Lock all records required at the beginning of a transaction Two-phase locking protocol Two-phase locking protocol Growing phase Growing phase Shrinking phase Shrinking phase May be difficult to determine all needed resources in advance May be difficult to determine all needed resources in advance Deadlock Resolution: Deadlock Resolution: Allow deadlocks to occur Allow deadlocks to occur Mechanisms for detecting and breaking them Mechanisms for detecting and breaking them Resource usage matrix Resource usage matrix

42. Chapter 12 © 2007 by Prentice Hall 42 Versioning Optimistic approach to concurrency control Optimistic approach to concurrency control Instead of locking Instead of locking Assumption is that simultaneous updates will be infrequent Assumption is that simultaneous updates will be infrequent Each transaction can attempt an update as it wishes Each transaction can attempt an update as it wishes The system will reject an update when it senses a conflict The system will reject an update when it senses a conflict Use of rollback and commit for this Use of rollback and commit for this

43. Chapter 12 © 2007 by Prentice Hall 43 Figure 12-15 The use of versioning Better performance than locking

44. Chapter 12 © 2007 by Prentice Hall 44 Managing Data Quality Causes of poor data quality Causes of poor data quality External data sources External data sources Redundant data storage Redundant data storage Lack of organizational commitment Lack of organizational commitment Data quality improvement Data quality improvement Perform data quality audit Perform data quality audit Establish data stewardship program (data steward is a liaison between IT and business units) Establish data stewardship program (data steward is a liaison between IT and business units) Apply total quality management (TQM) practices Apply total quality management (TQM) practices Overcome organizational barriers Overcome organizational barriers Apply modern DBMS technology Apply modern DBMS technology Estimate return on investment Estimate return on investment

45. Chapter 12 © 2007 by Prentice Hall 45 Data Dictionaries and Repositories Data dictionary Data dictionary Documents data elements of a database Documents data elements of a database System catalog System catalog System-created database that describes all database objects System-created database that describes all database objects Information Repository Information Repository Stores metadata describing data and data processing resources Stores metadata describing data and data processing resources Information Repository Dictionary System (IRDS) Information Repository Dictionary System (IRDS) Software tool managing/controlling access to information repository Software tool managing/controlling access to information repository

46. Chapter 12 © 2007 by Prentice Hall 46 Figure 12-16 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.

47. Chapter 12 © 2007 by Prentice Hall 47 Database Performance Tuning DBMS Installation DBMS Installation Setting installation parameters Setting installation parameters Memory Usage Memory Usage Set cache levels Set cache levels Choose background processes Choose background processes Input/Output (I/O) Contention Input/Output (I/O) Contention Use striping Use striping Distribution of heavily accessed files Distribution of heavily accessed files CPU Usage CPU Usage Monitor CPU load Monitor CPU load Application tuning Application tuning Modification of SQL code in applications Modification of SQL code in applications

48. Chapter 12 © 2007 by Prentice Hall 48 Data Availability Downtime is expensive Downtime is expensive How to ensure availability How to ensure availability Hardware failures–provide redundancy for fault tolerance Hardware failures–provide redundancy for fault tolerance Loss of data–database mirroring Loss of data–database mirroring Maintenance downtime–automated and nondisruptive maintenance utilities Maintenance downtime–automated and nondisruptive maintenance utilities Network problems–careful traffic monitoring, firewalls, and routers Network problems–careful traffic monitoring, firewalls, and routers