Retain

You might encounter a few applications in your on-premises environment that are essential for your business but are not suitable for migration because of technical reasons, such as the OS/application not being supported on a cloud platform. In such situations, your application cannot be migrated to the cloud, but you can continue running it in your on-premises environment.

For such servers and applications, you may need to perform only the initial analysis to determine their suitability for cloud migration. However, the server or application may still have dependencies with applications that are migrated. Therefore, you may have to maintain the connectivity of these on-premises servers to your cloud environment. You will learn more about on-premises to cloud connectivity in the Creating a hybrid cloud architecture section of this chapter.

Some typical workload examples for retentions are as follows:

• The legacy application where the customer doesn't see the benefit of moving to the cloud.
• The operating system or application support is not available in the cloud such as AS400 and mainframe application.

You may want to retain complex legacy systems to on-premise and prioritize them so that they can be moved a later point; however, during discovery, often, organizations find applications that are not in use anymore but still sitting around and consuming infrastructure space. You can choose to retire such applications. Let's explore more about the retiring strategy.