Maintenance Cycle 
Project cycle that was enhanced to meet the special requirements of maintenance projects. A maintenance cycle is represented by a generated task list and a transaction that is used only for the maintenance cycle. Together, they are called the maintenance cycle. The transaction type for this transaction is SMMN in the standard system. The transaction is used to set and shift project phases, for example.
The maintenance of a project landscape is described by an SAP Solution Manager project of the type maintenance. The lifecycle of a maintenance project is divided into maintenance cycles. Within a maintenance cycle, all changes are implemented and tested. At the end of the maintenance cycle, all these changes are imported into the production systems. In contrast to a development project, a maintenance project has a defined start. But since maintenance is an ongoing processes, the individual phases of the maintenance cycle can be passed through time and again.
After the completion of the implementation project, you assign your solution a maintenance project with a maintenance cycle so that the solution can be kept up to date.
The maintenance cycle follows the same phase model as the project cycle but has the following particularities:
Working with urgent changes
In maintenance operation, messages regarding incidents that have to be resolved quickly can occur at any time, for example, when the production systems could fail. In this case, a normal change does not enable you to respond quickly enough because it depends on the phase of the maintenance cycle. That means that if the maintenance cycle is in the Development without Release phase, you cannot enter any new changes for this cycle.
Urgent changes have their own task list, which means they can be transported irrespective of the phase of the assigned maintenance cycle (with the exception of the go live phase). You can import corrections for an urgent change into the production systems before the normal changes are imported in the go live phase of the maintenance cycle.
We recommend assigning a solution a maintenance project that runs as long as the solution is operated. Within the maintenance project, all necessary changes are covered by maintenance cycles. The change manager specifies the duration of a maintenance cycle, for example, one month. During this time, the cycle runs through all project phases from Development Without Release to Go Live. At the end of the go live phase, the cycle finishes. At this time, the cycle is checked for open and incomplete transactions and transport requests. Incomplete transactions are copied into a new maintenance cycle when one is created.
Structure
For information about assignment blocks, see Project Cycle.