# Global Namespace

> This guide covers everything about Global Namespaces within the Temporal Platform.

This page provides an overview of Global Namespace.

## What is a Global Namespace? 

A Global Namespace is a [Namespace](/namespaces) that exists across Clusters when [Multi-Cluster Replication](/temporal-service/multi-cluster-replication) is set up.

- [How to register a Global Namespace](/cli/command-reference/operator#create)
- [How to change the active Cluster for a Global Namespace](/cli/command-reference/operator#update)

The Global Namespace feature enables Workflow Executions to progress through another Cluster in the event of a failover.

A Global Namespace may be replicated to any number of Clusters, but is active in only one Cluster at any given time.

For a failover to be successful, Worker Processes must be polling for Tasks for the Global Namespace on all Clusters.

A Global Namespace has a failover version.
Because a failover can be triggered from any Cluster, the failover version prevents certain conflicts from occurring if a failover is mistakenly triggered simultaneously on two Clusters.

Only the active Cluster dispatches [Tasks](/tasks#task); however, certain conflicts are possible.
Unlike regular Namespaces, which provide at-most-once semantics for an Activity Execution, Global Namespaces can support only at-least-once semantics (see [Conflict resolution](/temporal-service/multi-cluster-replication#conflict-resolution)).
Worker Processes on the standby Clusters are idle until a failover occurs and their Cluster becomes active.

Temporal Application API calls made to a non-active Cluster are rejected with a **NamespaceNotActiveError** which contains the name of the current active Cluster.
It is the responsibility of the Temporal Application to call the Cluster that is currently active.