# What is meant by logical clock?

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## How does a logical clock work?

A Lamport logical clock is a numerical software counter value maintained in each process. Conceptually, this logical clock can be thought of as a clock that only has meaning in relation to messages moving between processes. When a process receives a message, it re-synchronizes its logical clock with that sender.

## What is the logical clock describe the important conditions to be satisfied by Lamport’s logical clock?

Logical Clock: The criteria for the logical clocks are: [C1]: Ci (a) < Ci(b), [ Ci -> Logical Clock, If ‘a’ happened before ‘b’, then time of ‘a’ will be less than ‘b’ in a particular process. ]

## What is Hybrid logical clock?

Solution. Hybrid Logical Clock provides a way to have a version which is monotonically increasing just like a simple integer, but also has relation with the actual date time. … It maintains the latest time as an instance of the hybrid timestamp, which is constructed by using system time and an integer counter.

## What is the use of logical clock?

A logical clock is a mechanism for capturing chronological and causal relationships in a distributed system. Often, distributed systems may have no physically synchronous global clock.

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## What is difference between logical clock and vector clock?

Most of the physical clocks are based on cyclic processes such as a celestial rotation. … In such systems a logical clock allows global ordering on events from different processes. Vector clock. It is an algorithm for generating a partial ordering of events in a distributed system.

## What are the advantages of vector clock?

Vector Clocks represent an extension of Lamport Timestamps in that they guarantee the strong clock consistency condition which (additionally to the clock consistency condition) dictates that if one event’s clock comes before another’s, then that event comes before the other, i.e., it is a two-way condition.

## What is physical clock?

A physical clock is a physical process coupled with a method of measuring that process to record the passage of time. … Most physical clocks are based on cyclic processes (such as a celestial rotation). One or more physical clocks are used to establish a time-line clock for a temporal database.

## What is the limitation of Lamport’s clock?

Lamport’s clock has the advantage of requiring no changes in the behavior of the underlying protocol, but has the disadvantage that clocks are entirely under the control of the logical-clock protocol and may as a result make huge jumps when a message is received.

## What is Lamport algorithm?

Lamport’s Distributed Mutual Exclusion Algorithm is a permission based algorithm proposed by Lamport as an illustration of his synchronization scheme for distributed systems. … In this algorithm: Three type of messages ( REQUEST, REPLY and RELEASE) are used and communication channels are assumed to follow FIFO order.

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