In the Enterprise Manager context, a manageable entity is an entity that Enterprise Manager is capable of managing.
A manageable entity can be in multiple states,
- Not-Yet Managed (NYM) state
- Managed state
- Existence only state
+ Initially when a target is discovered, it is loaded into the Management Repository as an NYM entity. In this state, the entity is not managed by a Management Agent yet.
+ The user can go to the discovery results page and assign them to a Management Agent along with required credentials. The entity then goes to managed state.
+ A discovered entity that Oracle does not support will have an existence only state. It is similar to an NYM entity except that it cannot be managed by Oracle.
+ Promotion refers to the process of converting unmanaged hosts and targets, which have been discovered in your network, to managed hosts and targets in Cloud Control so that they can be monitored and managed efficiently.
You can refer to below MOS note which covers the Host and Agent Target Promotion Flow and covers some steps to troubleshoot,
EM 12c: Troubleshooting Issues related to Missing / Status Pending / Metric Collection Error for Host or Agent Targets after Agent installation (Doc ID 1595464.1)