ITPEC IP October 2025 Question 29

Which of the following is the appropriate purpose of exclusive control in a database management system?

a)To ensure that data is not accidentally modified nor intentionally tampered withb)To make system maintenance management easy by making data and programs independent of each otherc)To prevent access to data except by certain persons according to the confidentiality of the datad)To prevent the occurrence of inconsistencies in data when multiple programs simultaneously access the same data

Explanation

Preventing inconsistencies when multiple programs access the same data at once — that is the purpose of exclusive control (locking).

If two programs both read a stock of 10 and each subtracts 1, both write back 9 and one update is lost. With exclusive control the first program locks the record; the second waits until the lock is released and then reads the updated 9, so the result is 8 and the data stays consistent. A shared lock lets several readers in together; an exclusive lock admits one updater only.

Answer (d)

Why not others:

•(a) — guarding data against accidental change and deliberate tampering is integrity in the security sense, kept by access rights, backups and tamper detection, not by locking
•(b) — separating data from programs so that one can change without the other is data independence, provided by the DBMS's schema structure
•(c) — letting only certain persons see data according to its confidentiality is access control (authorization)

Key rule: Exclusive control decides when a user may update (one at a time), access control decides who may; locking can in turn cause deadlock, which the DBMS must detect.

Databases · AI-written, may contain errors

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