Cutover runbook

As noted previously, migrations can be complex, with many moving parts that span hardware, software, people, processes, and organization. To ensure success, consistency, and eventual acceleration, a well laid out plan that is documented and agreed to by all stakeholders is essential across all stages of migration. Such a plan can be documented by using a cutover runbook.

A cutover runbook covers all the activities that must be completed for a given migration. It is a comprehensive and detailed guide of the following:

• Activities

• Planned timeline

• Actual activity timestamps

• Success criteria for each step

• Ownership for each step

When preparing the cutover runbook, ask yourself the following questions and provide the answers in your plan.

Question	Why it is important
Does the cutover need a downtime?	Extended downtime will impact your users' experience. When preparing your cutover plan, try to minimize the downtime of your application or system.
Do you need to synchronize the data before the cutover?	If you migrate the storage layer, such as Amazon Elastic Block Store (Amazon EBS) volumes or Amazon Simple Storage Service (Amazon S3) buckets before the cutover without using a continuous replication mechanism, the storage layer might get out of sync. In such cases, make sure to do a final sync after you shut down the source services but before you start the cutover.
Who should be aware of the planned cutover?	Notify all stakeholders and users about the planned downtime.
Do you want to split the migration into smaller parts or migrate everything at once?	If you migrate a complicated system, it makes sense to split the migration into phases and perform several cutovers. For example, you can migrate the data layer first.
Do you need any external vendor support?	You might need to contact the external vendors several weeks ahead of your planned cutover to ensure their availability. Check with the vendor about any licensing considerations to be aware of.
Do you need any special approval for any part of the process?	Get any required approvals a few weeks before the planned cutover.