What is consistent global state?

What is consistent global state?

A consistent global state is one corresponding to a consistent cut. These definitions correspond exactly to the intuition that consistent global states are those that could occur during a run in the sense that they could be constructed by an idealized observer external to the system.

What is consistent system state?

More precisely, a consistent system state is one in which if a process’s state reflects a message receipt, then the state of the corresponding sender reflects sending that message. The arrows represent directed channels between the nodes over which messages can be sent.

How do you ascertain a global state?

To determine a global system state, a process p must enlist the cooperation of other processes that must record their own local states and send the recorded local states to p. All processes cannot record their local states at precisely the same instant unless they have access to a common clock.

What is Transitless global state?

A “transitless” global state is one where each message that has been sent has been received. When the process has received from each neighbor a message that was sent after T, it makes its checkpoint permanent.

What is consistent cut?

Consistent Cuts. • Snapshot of global state in a distributed system. • Defined as snapshots where no event after the cut happened. before an event before the cut. • Forbids situations where effect is seen without its cause.

What is the requirements of global state in distributed system?

A global state of a distributed transaction system is consistent if no transactions are in progress. A global checkpoint is a transaction which must view a globally consistent system state for correct operation.

What is global clock in distributed system?

It is a mechanism for capturing causal and chronological relationships in a distributed system. A physically synchronous global clock may not be present in a distributed system. In such systems a logical clock allows global ordering on events from different processes.

What is the difference between a consistent and an inconsistent cut?

The cut events in a consistent cut are not causally related. Thus, the cut is a set of concurrent events and a set of concurrent events is a cut. Note, in this inconsistent cut, c3 –> c2. because this implies that no message sent after cut event ci has been received before some other cut event cj.

What are the 2 design issues of deadlock detection?

Detection of deadlocks involves addressing two issues: Maintenance of the WFG and searching of the WFG for the presence of cycles (or knots).

What are the fundamental concepts of consistent global states?

Consistent Global States of Distributed Systems: Fundamental Concepts and Mechanisms CS 249 Project Fall 2005 Wing Wong Consist Global States Outline Introduction Asynchronous distributed systems, distributed computations, consistency Two different strategies to construct global states

Is the global state of a distributed system consistent?

Even though each such global state may be consistent and the processes may be evaluating the same predicate, the different processes may executeconflicting reactions. This “relativistic effect” is inherent to all distributed computations and limits the class of system properties thatcan be effectively detected.

What is consist of global states in SJSU?

Consist Global States Distributed Computations. distributed program executed by a collection of processes each process executes a sequence of events communication through events send(m) and receive(m), m as message identifier. Consist Global States Distributed Computations.