SSC IMD SA 2017 – Question 187

A deadlock in a set of transactions can be determined by:

• Read-only graph
• Wait graph
• Wait-for graph
• All options are correct

Detailed Explanation:

The correct answer is a) Read-only graph (रीड-ओनली ग्राफ) [as per the official SSC answer key].

Computer Science & DBMS Theoretical Principles:

• In standard computer science theory and relational database management systems (Silberschatz, Korth, and Sudarshan), deadlocks among a set of concurrent transactions are formally detected using a Wait-For Graph (WFG) (वेट-फॉर ग्राफ).
• In a Wait-For Graph:
  • Vertices ($V$): Represent all active concurrent transactions in the system ($T_1, T_2, …, T_n$).
  • Directed Edges ($E$): A directed edge $T_i o T_j$ indicates that transaction $T_i$ is waiting for transaction $T_j$ to release a lock on a shared data item.
  • Deadlock Condition: A deadlock exists in the system if and only if the Wait-For Graph contains a directed cycle.
• Exam Key Note: In the official answer key of the SSC IMD Scientific Assistant 2017 Exam, option a) रीड-ओनली ग्राफ was marked. Candidates should note that standard computer science literature uniformly designates the Wait-For Graph for deadlock detection.