---
title: "Short note: Distributed cut"
subject: "Distributed System"
chapter: 5
key: "semester_7/distributed_system:distributed-cut-note"
source: https://www.bctengineer.com/q/semester_7/distributed_system/distributed-cut-note
site: BCT Engineering
---

# Short note: Distributed cut

Distributed System · Chapter 5: Time and State in Distributed Systems

- Asked in: 2074 Chaitra, 2 marks
- Video: [Global state in Distributed Systems, Consistent and Inconsistent cuts](https://www.youtube.com/watch?v=wiBWIdV8Eec) — Simplified Computer Science Concepts-Prof. Rutuja
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/distributed_system/distributed-cut-note
- Whole chapter: https://www.bctengineer.com/md/semester_7/distributed_system/chapter-5

## Question

Write a short note on distributed cut.

## Short answer

A distributed cut is a prefix of each process's history, representing a global state. A consistent cut includes all events that happened before any included event, so no message is received whose send is outside the cut. Inconsistent cuts violate this, making them impossible states. Consistent cuts are used in snapshots and debugging.

## Answer

A **distributed cut** is a set of events, taking a prefix of the history of each process, that represents a possible global state. Its boundary (a line across the process time-lines) is called the cut frontier.

- **Consistent cut**: if an event e is in the cut, every event that happened before e is also in it. No message is received inside the cut while its send lies outside. It represents a state the system could really have been in.
- **Inconsistent cut**: includes a receive event without its send, so it cannot occur in real execution.

Consistent cuts are used in checkpointing, snapshot algorithms (Chandy-Lamport), deadlock and termination detection, and debugging.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is a distributed cut?
   A. A single event
   B. A message in transit
   C. A hardware clock reading
   D. A set of events forming a prefix of each process's history
   Answer: D. It represents a possible global state. (Key point: Cut definition)

2. Which condition makes a cut consistent?
   A. No message is received inside the cut with its send outside
   B. Every process has the same number of events
   C. All messages are in transit
   D. No send is in the cut
   Answer: A. The cut then represents a state the system could really have been in. (Key point: Consistent cut)

3. Which is a use of consistent cuts?
   A. Compiling IDL
   B. Checkpointing and snapshot algorithms like Chandy-Lamport
   C. Setting clocks to UTC
   D. Selecting NTP strata
   Answer: B. Consistent cuts underpin checkpointing, deadlock/termination detection and debugging. (Key point: Use)

## Related in Distributed System

- [State recording, debugging, distributed cuts](https://www.bctengineer.com/question.md?key=semester_7%2Fdistributed_system%3Astate-recording-cut) — Distributed System, chapter 5