// Module included in the following assemblies:
//
// * updating/updating_a_cluster/updating_disconnected_cluster/disconnected-update-osus.adoc

:_mod-docs-content-type: CONCEPT
[id="update-service-overview_{context}"]
= Using the OpenShift Update Service in a disconnected environment

[role="_abstract"]
The OpenShift Update Service (OSUS) provides update recommendations to {product-title} clusters. Red{nbsp}Hat publicly hosts the OpenShift Update Service, and clusters in a connected environment can connect to the service through public APIs to retrieve update recommendations.

However, clusters in a disconnected environment cannot access these public APIs to retrieve update information. To have a similar update experience in a disconnected environment, you can install and configure the OpenShift Update Service so that it is available within the disconnected environment.

A single OSUS instance is capable of serving recommendations to thousands of clusters.
OSUS can be scaled horizontally to cater to more clusters by changing the replica value.
So for most disconnected use cases, one OSUS instance is enough.
For example, Red{nbsp}Hat hosts just one OSUS instance for the entire fleet of connected clusters.

If you want to keep update recommendations separate in different environments, you can run one OSUS instance for each environment.
For example, in a case where you have separate test and stage environments, you might not want a cluster in a stage environment to receive update recommendations to version A if that version has not been tested in the test environment yet.

The following sections describe how to install an OSUS instance and configure it to provide update recommendations to a cluster.