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OKD 4 clusters are different from OKD 3 clusters. OKD 4 clusters contain new technologies and functionality that result in a cluster that is self-managing, flexible, and automated. To learn more about migrating from OKD 3 to 4 see About migrating from OpenShift Container Platform 3 to 4.

Differences between OKD 3 and 4

Before migrating from OKD 3 to 4, you can check differences between OKD 3 and 4. Review the following information:

Planning network considerations

Before migrating from OKD 3 to 4, review the differences between OKD 3 and 4 for information about the following areas:

You can migrate stateful application workloads from OKD 3 to 4 at the granularity of a namespace. To learn more about MTC see Understanding MTC.

Upgrading MTC

You upgrade the Migration Toolkit for Containers (MTC) on OKD 4.12 by using OLM. You upgrade MTC on OKD 3 by reinstalling the legacy Migration Toolkit for Containers Operator.

Reviewing premigration checklists

Before you migrate your application workloads with the Migration Toolkit for Containers (MTC), review the premigration checklists.

Migrating applications

You can migrate your applications by using the MTC web console or the command line.

Advanced migration options

You can automate your migrations and modify MTC custom resources to improve the performance of large-scale migrations by using the following options:

Rolling back a migration

You can roll back a migration by using the MTC web console, by using the CLI, or manually.

Uninstalling MTC and deleting resources

You can uninstall the MTC and delete its resources to clean up the cluster.