DBMS MODULE 1

Data

Raw unprocessed facts such as numbers, characters, images, videos.

Database

Logically coherent collection of data with inherent meaning.

DBMS

Collection of interrelated data + programs to manage and access data.

Enterprise database applications

Used in sales, HR, accounting, manufacturing, and ecommerce.

Banking database applications

Manages customer accounts, loans, transactions, credit card statements.

University database applications

Stores student details, registrations, grades.

Airline database applications

Manages schedules and reservations.

Telecom database applications

Maintains call logs, billing, balances, network data.

Data redundancy

Same data stored in multiple files leading to wasteful storage.

Data inconsistency

Mismatch between copies of the same data across files.

Difficulty accessing data

File system requires new programs for every new requirement.

Data isolation

Data stored in many formats making retrieval difficult.

Integrity problem

Hard to enforce or update rules when constraints change.

Atomicity problem

Transaction must complete fully or not at all; failures cause inconsistency.

Concurrent access anomaly

Multiple simultaneous updates cause incorrect results.

Security problems

File systems do not restrict unauthorized access.

1-tier architecture

User interacts directly with DBMS.

2-tier architecture

Application layer communicates with the database for the user.

3-tier architecture

Presentation, application, and database layers separated.

Physical level

Describes physical storage of data on disk.

Logical level

Describes data stored and relationships among them.

View level

User-specific representation of data.

Physical data independence

Physical schema changes do not affect logical schema.

Logical data independence

Logical schema changes do not affect user views.

DDL

Language for defining database schema.

DML

Language used to retrieve, insert, delete, and update data.

Procedural DML

User specifies what data is required AND how to get it.

Nonprocedural DML

User specifies only what data is required.

Query language

Subset of DML for data retrieval.

Application programmers

Use embedded DML inside host languages.

Sophisticated users

Write database queries directly.

Specialized users

Use complex applications like CAD, expert systems.

Naive users

Use permanent application programs such as ATM interface.

DBA

Person with central control over the database system.

DBA - installation

Installs DBMS and related software.

DBA - configuration

Coordinates with system admin to configure hardware/software.

DBA - security

Manages users, permissions, auditing.

DBA - data analysis

Recommends indexing and performance tuning.

DBA - preliminary design

Assists early database design to avoid issues.

File manager

Manages disk space and low-level storage structures.

Database manager

Enforces integrity, security, concurrency, recovery.

Query processor

Analyzes and converts queries into low-level instructions.

DML precompiler

Converts DML in host languages into procedure calls.

DDL compiler

Converts DDL commands into metadata stored in data dictionary.

Data dictionary

Stores metadata (data about data).

Indices

Provide fast access paths to data.

Schema

Overall database design.

Instance

Snapshot of the database at a particular time.

Cardinality

Number of rows in a relation.