For this upgrade mode there is some automatic upgrade behaviour built into the upgrade framework. This is provided by the ServerUpgrade class. If your upgrade consists of any of the following operations then you may find there is no need to create an upgrade step:
- Service Addition
- Service Removal
- Attribute Addition
- Attribute Removal TODO - there may be more.
For all other options you will need to define an upgrade step that performs the schema and configuration changes. There are numerous examples in the org.forgerock.openam.upgrade.steps package to learn from.
Related Developer Question: How do define an upgrade step?