chap12.ppt

TM 13-TM 13-11Copyright © Addison Wesley Longman, Inc. & Copyright © Addison Wesley Longman, Inc. & Dr. ChenDr. Chen, , Business Database SystemsBusiness Database Systems

Chapter 12Data and Database Administration

Jason C. H. Chen, Ph.D.Professor of MIS

School of Business AdministrationGonzaga UniversitySpokane, WA [email protected]


Objectives• Introduce students to the principles and tools of

data administration and its relationship to information resource management.

• Understand the problems of database security and the techniques used to enhance database security.

• Understand database recovery and the available procedures and facilities to use when recovery is necessary.


Data (Resource) Administration

• Data (resource) administration (DRA) activities have been developed to help achieve organizations’ goals for the effective management of data.

• Effective DRA provides support for managerial decision making at all levels in the organization. On other hand, ineffective DRA, leads to poor data utilization.


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 (a managerial function)

• 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.


Data Administration Functions

• Data policies, procedures, standards.• Planning.• Data conflict (ownership) resolution.• Internal marketing of DA concepts.• Managing the data repository.• Providing education, training, and

consulting support to users.


Database Administration Functions

• Selection of hardware and software• Installing/upgrading DBMS• Tuning database performance• Improving query processing performance• Managing data security, privacy, and integrity• Data backup and recovery• Fig. 12-1is a list of DA and DBA functions (all

phases in the database development).


Life Cycle Phases of DA and DBADatabase Planning

Database Analysis

Database Implementation

Database Design

Operations and Manintenance

Growth and Change


Database planningDevelop corporate database strategyDevelop enterprise modelDevelop cost/benefit modelsDevelop database environmentDevelopment data administration plan

Database analysisDefine and model data requirementsDefine and model business rulesDefine operational requirementsMaintain corporate data dictionary

Database designPerform logical database designDesign external mode (subschemas)Design internal modelsDesign integrity controls

Data implementationSpecify database access policiesEstablish security controlsSupervise database loadingSpecify test proceeduresDevelop application programming standardsEstablish procedures for backup and recovery

Operations and maintenanceMonitor database performanceTune and reorganize databasesEnforce standards and proceduresSupport users

Growth and changeImplement change-control proceduresPlan growth and changeEvaluate new technology

Conduct user training

DA

DBA

DA/DBA

DBA

DA/DBA

DBA

DA/DBA

Life-Cycle Phase

Function DA = typically performed by data administrationDBA= typically performed by database administration

Figure 12-1

Functions of data administration and database administration


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

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

metadata/data across many data sources• Specific roles:

Support decision –support applications Manage data warehouse growth Establish service level agreements regarding data

warehouses and data marts


Database Security

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

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

• Fig. 12-2.


Fig. 12-2: Possible locations of data security threats

Database

Firewall


Threats to Data Security (and they must be addressed in a

comprehensive data security plan)• 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 Management Software Security Features

• Views or subschemas• Integrity controls• Authorization rules• User-defined procedures

E.g. trigger an authorization procedure which asks additional identification questions(Oracle).

• Encryption• Authentication schemes

Biometric devices, voice, eye, finger printing• Backup, journalizing, and checkpointing


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 Domains – set allowable values Assertions – enforce database conditions


Authorization Rules• Controls incorporated in the data management systemRestrict:

access to data actions that people can take on data

Authorization matrix for: Subjects Objects Actions Constraints


Figure 12-3: Authorization matrix


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

Figure 12-4(a): Authorization table for subjects

Figure 12-4(b): Authorization table for objects

Figure 12-5: Oracle8i privileges


Authentication Schemes• Goal – 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 in Unencrypted passwords travel the Internet

• Possible solutions: Biometric devices – use of fingerprints, retinal scans, etc. for

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

certificates


Database Recovery

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

• Recovery facilities: Backup Facilities Journalizing Facilities Checkpoint Facility Recovery Manager


Backup Facilities• 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 is shut down

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


Journalizing Facilities• Audit trail of transactions and database updates• Transaction log – record of essential data for each

transaction processed against the database time, records, input values.

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

Produces an audit trail (Fig. 12-6)audit trail (Fig. 12-6)


Figure 12-6: Database audit trail

contains a record of the essential data for each transaction that is processed against the database.

contains before- and after- images of records that have been modified by transactions.


Checkpoint Facilities

• DBMS periodically refuses to accept new transactions system is in a quiet state

• Database and transaction logs are synchronized

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


Recovery and Restart Procedures• Switch - Mirrored databases.• Restore/Rerun - Reprocess transactions against

the backup.• Transaction Integrity - Commit or abort all

transaction changes.• Backward Recovery (Rollback) - Apply before

images (Fig. 12-7a)• Forward Recovery (Roll Forward) - Apply

after images (preferable to restore/rerun.) (Figure 12-7b)


Fig. 13-7:Basic recovery techniques(a) Rollback


Fig. 13-7: (b) Rollforward


Types of Database Failure• Aborted transactions

due to human error, input of invalid data, hardware failure, and deadlock

• Incorrect data (but is valid)• System failure (database is not damaged)

due to power loss, operator error, loss of communications transmission, and system software failure

• Database destruction - data base is lost, destroyed, or can’t be read due to disk drive failure (or head crash)


Responses to Database Failure (Table 12-1)

Recovery TechniqueRollback (preferred)Rollforward/return transactions to state just priorto abort

Rollback (preferred)Reprocess transactions without inaccurate(but is difficult) data updatesCompensating transactions

Switch to duplicate database (preferred) -- for mirrored databaseRollbackRestart from checkpoint - for not mirrored d.b.

Switch to duplicate database (preferred) -- for mirrored databaseRollforwardReprocess transactions

1. Aborted transaction

2. Incorrect data(update/enter inaccurately)

3. System failure (database intact)

4. Database destruction

Type of Failure


BreakExercises Study (p.488)#4

HW: #3


Concurrency Control• ProblemProblem – in a multi-user environment,

simultaneous access to data can result in interference and data loss

• SolutionSolution – 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.


Fig. 12-8: Lost update (no concurrency control in effect)

Time

Marsha

ERROR!

John

1. Read account balance (Balance = $1,000)

2. Withdraw $200 (Balance = $ 800)

3. Write account balance (Balance = $800)

1. Read account balance (Balance = $1,000)

2. Withdraw $300 (Balance = $700)

3. Write account balance (Balance = $700)

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


Concurrency Control Techniques (conti.)• Serializability

Finish one transaction before starting another.• Locking Mechanisms

The most common way of achieving serialization Data that is retrieved for the purpose of updating is locked for the updater No other user can perform update until unlocked enforce a sequential updating process that prevents erroneous updates (Fig. 12-9)

• Locking level: Database – used during database updates Table – used for bulk updates Block or page – very commonly used Record – only requested row; fairly commonly used Field – requires significant overhead; impractical


Fig. 12-9:Updates with locking (concurrency control)

Time John1. Read account balance2. Lock account balance3. Read account balance (Balance $1,000)4. Withdraw $200 (Balance = $ 800)5. Write account balance (Balance = $800)6. Unlock account balance

Marsha

1. Request account balance (denied)

2. Lock account balance3. Read account balance (Balance = $800)4. Withdraw $300 (Balance = $500)5. Write account balance (Balance = $500)6. Unlock account balance

This prevents the lost update problem


• Types of locks: Shared lock (S locks or read locks)

Read but not update permitted. Used when just reading to prevent another user from placing an exclusive lock on the record.

Exclusive lock (X locks, or write locks)No access permitted. Used when preparing to

update. Purpose of the lock

maintain data integrity

Concurrency Control Techniques (Cont.)


Deadlock• Deadlock:

An impasse that results when two or more transactions have locked a common resource, and each waits for the other to unlock that resource (Fig. 12-10, 11.)


Fig. 12-10: The problem of deadlock

Time John1. Place read/S lock

2. Check balance (Balance = $1,000)

Marsha

1. Place read/S lock

2. Check balance (Balance = $1,000)

If a record is a read/S lock

3. Request write lock(denied)

Deadlock!

3. Request write lock (denied) Another user can’t

obtain a write lock

WAIT

WAIT


Fig. 12-11: Another example of deadlock

Time User A

1. Lock record X

User B

1. Lock record Y

Deadlock!

2. Request record Y 2. Request record X

(Wait for Y) (Wait for X)

UserA and UserB will wait UserA and UserB will wait forever for each other to forever for each other to release their locked release their locked resources!resources!


Managing Deadlock• Deadlock prevention:

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

Growing phase (all necessary locks are acquired)Shrinking phase (where all locks are released)

May be difficult to determine all needed resources in advance

• Deadlock Resolution: Allow deadlocks to occur Mechanisms into DBMS for detecting and breaking them

Resource usage matrixWhat subjects(users) are using What objects (resources)


Concurrency Control Techniques (Cont.)• Versioning:

An optimistic approach to concurrency control that there is no form of locking and DBMS creates a new record version instead of overwriting the old record.

Assumption is that simultaneous updates will be infrequent and requires no form of locking.

The system will reject an update when it senses a conflict and creates a new record version instead of overwriting the old record.

Each transaction can attempt an update as it wishes. Use of rollback and commit for this Fig. 12-12.


Fig. 12-12: The Use of versioningTime

John

1. Read balance (Balance = $ 1,000)

2. Withdraw $200 (Balance = $800)

3. Commit

Marsha

1. Read balance (Balance = $1,000)

2. Attempt to withdraw $300 (Denied /Rejected-balance-update dut to conflict)

3. Rollback

4. Restart transaction

Better performance than locking


Managing Data Quality• Data Steward - Liaisons (a person) between IT and

business units (enterprise goals)• Five Data Quality Issues:

Security policy and disaster recovery. Personnel controls. Physical access controls. Maintenance controls (hardware & software.) Data protection and privacy.

• Ensure that data are accurate, consistent, and available in a timely fashion.


Data Dictionaries and Repositories

• Data dictionary: A repository of information about a database (metadata) that documents data elements of a database. It is a part of system catalog.

• System catalog: A system-created database that describes all database objects, including data dictionary information, but also includes user access information


SQL> select * from user_catalog;

TABLE_NAME TABLE_TYPE------------------------------ -----------BACKORDER TABLECOLOR TABLECOUNT_TABLE TABLECOURSE TABLECOURSE_SECTION TABLECUSTOMER TABLECUST_ORDER TABLEENROLLMENT TABLEFACULTY TABLEFACULTY_VIEW VIEWINVENTORY TABLEINVENTORYVIEW VIEWINVENTORY_VIEW VIEWINVID_SEQUENCE SEQUENCEITEM TABLELOCATION TABLEORDERLINE TABLEORDERSOURCE TABLESHIPPING TABLESTUDENT TABLETERM TABLE

TABLE_NAME TABLE_TYPE------------------------------ -----------TERM_VIEW VIEWYEAR_DATES TABLE

SQL> select * from user_catalog where table_name like 'T%';

TABLE_NAME TABLE_TYPE--------------- -----------TERM TABLETERM_VIEW VIEW

System Catalog in Oracle


SQL> COLUMN Object_Name format a27SQL> SQL> SELECT Object_Name, Created, Last_DDL_Time 2 FROM USER_OBJECTS;

OBJECT_NAME CREATED LAST_DDL_--------------------------- --------- ---------BACKORDER 12-APR-01 12-APR-01BACKORDER_BACKORDERID_PK 12-APR-01 12-APR-01COLOR 12-APR-01 12-APR-01COLOR_COLOR_PK 12-APR-01 12-APR-01COUNT_TABLE 28-MAR-01 28-MAR-01COURSE 07-MAR-01 07-MAR-01 …SYS_C0057532 07-MAR-01 07-MAR-01SYS_C0074691 12-APR-01 12-APR-01TERM 07-MAR-01 07-MAR-01TERM_TERMID_PK 07-MAR-01 07-MAR-01TERM_VIEW 07-MAR-01 07-MAR-01UPDATEENROLLMENT 19-FEB-01 19-FEB-01

SQL> SELECT Object_Name, Created, Last_DDL_Time 2 FROM USER_OBJECTS 3 WHERE Object_Name LIKE 'T%';

OBJECT_NAME CREATED LAST_DDL_--------------------------- --------- ---------TERM 07-MAR-01 07-MAR-01TERM_TERMID_PK 07-MAR-01 07-MAR-01TERM_VIEW 07-MAR-01 07-MAR-01

OTHER COMMANDS:(Systems_Catalog.SQLOracle8i - The Complete Reference, p.719)

SELECT Column_Name, Data_Typefrom USER_TAB_COLUMNSWHERE Table_Name = 'TERM';

SELECT View_name, Text_LengthFROM USER_VIEWSWHERE View_Name = 'TERM_VIEW';

SET long 500SELECT Text from user_viewsWHERE View_Name = 'TERM_VIEW';

column comments format a50select Table_name, Comments from DICTwhere Table_Name LIKE '%VIEWS%';


Data Dictionaries and Repositories (Cont.)

• Active data dictionary - managed by DBMS.• Passive data dictionary - managed by the user(s) of

the system.• Relational catalog.• Information Repository

Stores metadata describing data and data processing resources

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

repository (Fig. 12-13)


Fig. 12-13: Three components of repository system architecture.

InformationModel

Repository Engine:

Objects Relationships Extensible Version & Types Configuration Management

RepositoryDatabase

A schema of the repository information

Stored in the

Important forO-O develop.

N

(Where repository objectsare stored)

(Software that manages the repository objects)


Tuning the Database for Performance

• Effective database support results in a reliable database where performance is not subject to interruption for H/S W or user problem and where optimal performance is achieved.

• However, tuning is an ongoing part of managing any database, as H/S W configurations change, and as user activity changes.


Database Performance Tuning• Five areas of DBMS management that should be addressed

when trying to maintain a well-tuned database are addressed: DBMS Installation

Setting installation parameters Memory Usage

Set cache levelsChoose background processes

Input/Output ContentionUse stripingDistribution of heavily accessed files

CPU UsageMonitor CPU load

Application tuningModification of SQL code in applications


End of Chapter 12

• An important chapter for a future database manager like you ...

Exercises Study (p.488)#3

HW: #1

chap12.ppt

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