The purpose of Service System Transition (SST) (CMMI-SVC) is to deploy new or significantly changed service system components while managing their effect on ongoing service delivery.
The Service System Transition process area addresses all aspects of planning, communicating, managing, deploying, and confirming that service system components effectively make the transition to the delivery environment. The scope of this process area covers both new components and significant changes to existing components.
“Significant” is defined as a change that introduces unacceptable risk that the service system will not meet its objectives. Although these practices center on the transition of service system components, the transition of an entire service system (i.e., an interdependent and integrated collection of components) can also be managed using these practices.
In this process area, the term “transition” refers to the comprehensive process of preparing for, executing, and confirming a deployment of service system components to a fully operational state while maintaining service delivery. The term “deploy” or “deployment” is more specific and refers to the activity of moving service system components into the delivery environment. In some domains, a deployment is also called a “roll-out.” Deployments generally fall into one of three categories:
- New installation
Transition planning ensures that relevant stakeholders are properly informed of upcoming changes. Preparing for transition also encompasses compatibility evaluations of the to-be service system within the current delivery environment as constrained by existing service agreements and ongoing service delivery activities. Impacts on a service system that will be replaced or phased out over time by a new service system are considered. Impacts on service systems that share interfaces or resources with a new one are also considered, as are impacts on service continuity.
Critical aspects of service system transition include the following:
- Configuration control of service system components
- Management of internal and external interfaces
- Deployment of service system components into the delivery environment
- Stakeholder acceptance of new or revised service system components
- Management of impacts of the transition
Emergency changes to a service system can be made when approved by a designated authority according to established policies. The normal, expected order of service system transition processes can be altered to accommodate the unique needs of an emergency situation, but all relevant processes should eventually be completed once the situation returns to normal. This approach allows any unanticipated impacts associated with emergency changes to be identified and addressed.