TCATCA

Section A : 40%Section A : 40%– Case studyCase study– Create ER Level 2 and attributesCreate ER Level 2 and attributes

Section B : 60%Section B : 60%– 30 Questions30 Questions– 2 marks correct answer2 marks correct answer– -1 mark deducted for an incorrect -1 mark deducted for an incorrect

answeranswer

TCATCA

January Monday 13January Monday 13th 1 - 2.30 th 1 - 2.30 N133A N133A

Modules TopicsModules Topics Data Modelling the ER ModelData Modelling the ER Model SQLSQL File OrganisationFile Organisation DBMSDBMS Relational AlgebraRelational Algebra Relational OptimizationRelational Optimization Integrity & SecurityIntegrity & Security Concurrency / RecoveryConcurrency / Recovery Networked & Distributed Networked & Distributed

SystemsSystems

Data Modelling the ER Data Modelling the ER ModelModel

Identify Entity's from a case studyIdentify Entity's from a case study Draw a ER Diagram level 1 and 2 & Draw a ER Diagram level 1 and 2 &

showing all relationshipsshowing all relationships

SQLSQL

SQL explanationSQL explanation

File OrganisationFile Organisation

BlockingBlocking– How is it used How is it used – Why is it used Why is it used – Calculation on disk utilisationCalculation on disk utilisation

File accessFile access– Type of indexesType of indexes

Dense vs. non-denseDense vs. non-dense

File OrganisationFile Organisation

– Direct access methodsDirect access methods HashingHashing Collisions, handling collisionsCollisions, handling collisions

– Dynamic data structuresDynamic data structures Linked listsLinked lists

– Inverted listsInverted lists Deletion, insertion & updating filesDeletion, insertion & updating files

DBMSDBMS

Maintenance of physical data Maintenance of physical data structures (files, indexes,etc)structures (files, indexes,etc)

Languages for storage, retrieval and Languages for storage, retrieval and update of the data (3GL’s, 4GL’s)update of the data (3GL’s, 4GL’s)

Facilities for ensuring data integrity Facilities for ensuring data integrity and securityand security

Support for multi-user access Support for multi-user access Backup and recovery measuresBackup and recovery measures

DBMSDBMS

Facilities for maintenance of meta-data Facilities for maintenance of meta-data (data dictionary or system catalogue)(data dictionary or system catalogue)

Data independence (logical view)Data independence (logical view) Tools for the database administratorTools for the database administrator

User InterfaceUser Interface Database EngineDatabase Engine Data DictionaryData Dictionary

Relational AlgebraRelational Algebra Compares strategies (Number of Compares strategies (Number of

Recs)Recs) SELECT (restrict SELECT (restrict aa(R)(R)))

– picks out particular Rowspicks out particular Rows PROJECT PROJECT a,ba,b(R)(R)

– picks out particular Columnspicks out particular Columns JOIN JOIN R |X| SR |X| S Draw Query Execution PlanDraw Query Execution Plan

– Choice of order, smaller temp tablesChoice of order, smaller temp tables

Relational OptimizationRelational Optimization Reasons for beingReasons for being Process involvedProcess involved

– Steps involved, Interpretation, ExecutionSteps involved, Interpretation, Execution PositionPosition

– Integrated in DBMS, Interactive SQL, Integrated in DBMS, Interactive SQL, reference to Data Dictionaryreference to Data Dictionary

Types Types – Rule BasedRule Based– Cost BasedCost Based

Security & IntegritySecurity & Integrity

What are the issues surrounding What are the issues surrounding security and integritysecurity and integrity

What security issues exist that have What security issues exist that have to be resolvedto be resolved

What measures are used to ensure What measures are used to ensure consistency of the databaseconsistency of the database

Why do we implement these Why do we implement these measuresmeasures

Concurrency and RecoveryConcurrency and Recovery

DefinitionsDefinitions ACID properties of transactionsACID properties of transactions Need for Concurrency / Need for Concurrency /

RecoveryRecovery– Lost update, Uncommitted Lost update, Uncommitted

Updates, Inconsistent AnalysisUpdates, Inconsistent Analysis– Crashes, Sabotage, Logical Crashes, Sabotage, Logical

errors...errors...

Recovery uses LOG fileRecovery uses LOG file

Format of LOG entryFormat of LOG entry– Transaction record, Check Transaction record, Check

pointspoints Incremental LogIncremental Log

– Deferred UpdatesDeferred Updates– Immediate UpdatesImmediate Updates

Concurrency TechniquesConcurrency Techniques

LocksLocks– Shared/Exclusive, Two phase lockingShared/Exclusive, Two phase locking– Problem of DeadlockProblem of Deadlock

TimestampsTimestamps– Compares timestamps of Compares timestamps of

transactionstransactions– Problem late transactionsProblem late transactions

OptimisticOptimistic– Used where few conflict expectedUsed where few conflict expected

Networked & Distributed Networked & Distributed SystemsSystems

What are distributed databasesWhat are distributed databases In what kind of situation are they In what kind of situation are they

suitablesuitable What advantages / disadvantages What advantages / disadvantages

to they have over centralised to they have over centralised systemssystems

Problems that can arise due to the Problems that can arise due to the use of DDBuse of DDB

Networked & Distributed Networked & Distributed SystemsSystems

Implementation issuesImplementation issues– ConcurrencyConcurrency– ReplicationReplication– Query processingQuery processing– TransparencyTransparency– FragmentationFragmentation