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  1. LPU MCA Semester 1
  2. CAP570
  3. Unit 1

CAP570 · Unit 1: Basics of database

Database architecture and components

10 practice questions · in the MTE and ETE syllabus

Practise this topicPractise this topic

Key points

  • Three levels: external, conceptual, internal
  • Mappings between levels give data independence
  • Buffer manager caches disk pages in memory
  • The DBA manages installation, security and backup

The ANSI-SPARC three-level architecture separates how users see data from how it is stored.

  • External level: many user views, each showing the part of the data a user group needs.
  • Conceptual level: one logical description of the whole database, its entities, relationships and constraints.
  • Internal level: physical storage, file organisation and access paths.

Mappings between the levels give data independence. Logical independence means a conceptual change need not alter external views or programs. Physical independence means a storage change need not alter the conceptual schema.

Main DBMS components: the DDL compiler (processes definitions into the catalog), the DML compiler and query processor (parse, optimise and plan queries), the storage manager with the buffer manager (moves pages between disk and memory), the transaction manager with concurrency control and the recovery manager, and the authorisation subsystem. The database administrator (DBA) installs the DBMS, grants rights and arranges backup.

Exam trap: physical independence concerns storage changes; logical independence concerns schema changes.

Try two questions

Question 1 · Tier 3, Apply

A table is moved to a faster disk and its file organisation is changed, yet no application program needs to be rewritten. Which property is shown?

  1. Strong logical data independence
  2. Referential integrity
  3. Physical data independence
  4. Isolation
Show the answer

C. Changes to the internal level that leave the conceptual schema and programs intact show physical data independence.

Why not A: Logical independence concerns changes to the conceptual schema, not storage.

Why not B: Integrity keeps foreign keys valid and is not about storage changes.

Why not D: Isolation is a transaction property, not about programs surviving storage changes.

Question 2 · Tier 3, Apply

A new column is added to a table at the conceptual level, yet existing user views and programs keep working unchanged. Which property is shown?

  1. Physical data independence
  2. Atomicity
  3. Durability
  4. Strong logical data independence
Show the answer

D. Changing the conceptual schema without disturbing external views or programs is logical data independence.

Why not A: That concerns storage structure changes, not the conceptual schema.

Why not B: Atomicity is a transaction property.

Why not C: Durability guarantees committed data survives failure, which is unrelated.