IS 4424: Developing the Entreprise Database

Frederic Adam

Course Content

• Data Modelling

• Analysing requirements

• Sizing

• Developing large DBs

• Administering the DB

• Other key issues (e.g. KM, DW etc…)

• Chosen Platform ORACLE

Oracle

• Industry standard• #1 pb: rate of change and upgrade• Complexity: manuals = 20,000 pages

– (error message manual = 1700 pages)

• DBs are at the core of most business applications– Knowledge of ORACLE is key for

developersORACLE is not a bucket in which you throw your data

Characteristics of DBs…

…which ORACLE features:

• High concurrency (high performance under load)

• Multi-user (read does not interfere with write)• Data consistency – changes to data don’t affect

running queries + no phantom data changes• High degree of recoverability (pull the plug test)

ACID test

• Atomicity

• Consistency

• Isolation

• Durability

ACID test

• Atomicity

• Consistency

• Isolation

• Durability

All or nothing

Preserve consistency of database

Transactions are independent

Once committed data is preserved

Why DB projects fail?

• Ignoring the technology (HW / SW)

• Estimating performance wrong

• Getting the sizing wrong

• Fudging the testing (Pareto principle)

• Confuse the responsibilities for DB

= ANALYSIS of pb

Analysis of Problem

• Data model

• Technical decisions (sizing / hardware…)

• Functionalities

• Interface

• ReportsTypes of decisions:NormalisationData access – indexesSecurity options (level; roles…)

Entity Relationship Model

• Entity

• Attributes

• Instance(s)

• Domain

• Key (candidate primary and foreign)

definitions

• Entity

• Attributes

• Instance(s)

• Domain

• Key (candidate primary and foreign)

Object in real world distinguishable from others

Description of entity – shared attributes

Range of possible values for attribute

Attribute that uniquely identified an entitySelected keyAttribute of one entity that is primary keyin another one

(Number of) occurrences of an entity

Relationship sets

• Relationship

• Ordinality

• Cardinality

• Associative Entity

Definitions (2)

Association of two or more entities

Entity whose attributes describean association between 2 entities

• Relationship

• Ordinality

• Cardinality

• Associative Entity

Minimum number of occurrence ofone entity relative another one –optionality or dependency

Maximum number…

Some test questions

• Is it a bird is it a plane?

• Is it an entity or an attribute?

Some test questions

• Is it a bird is it a plane?

• Is it an entity or an attribute?

No, it’s Superman

e.g. address[more than one per emp.?]Matter of analysis of thebusiness problem

From data modelling to DB design

• Ideally, one data structure = one schema

• But DBs not always developed in one go

• Organisations merge…

• Need to integrate schemas

• Difficult to anticipate and resolve conflicts (eg names…) = ERP projects

I/O Trap

• Reading existing data• Changing existing data

– Update existing records– Adding new records– Deleting records

• All these involve going to disk => slowest device by considerable margin

• Minimise / reschedule physical I/O