AWS customers now have the option to enable Systems Manager, and configure permissions for all EC2 instances in an organization that has been configured to use AWS Organizations, with a single action using Default Host Management Configuration (DHMC). This feature provides a method to help customers ensure core Systems Manager capabilities such as Patch Manager, Session Manager, and Inventory are available for all new and existing instances. DHMC is recommended for all EC2 customers, and offers a simple, scalable process to standardize the availability of System Manager tools.
Source:: Amazon AWS