SYMPTOM:
A user receives the following error when trying to run a report in Strategy Developer or Web:

Error: Error(s) occurred while loading schema: DSSSQLEngine: Schema loading error: Population Exception: The object shown in the following hierarchy no longer exists in schema: - Population Exception: DBMS-DBMSThe object definition is incomplete or inconsistent.
CAUSE:
This error occurs because one of the database instances that the project has assigned is incorrectly defined.
ACTION:
Edit the database instances for the project with the error and make sure that they have a Database Connection Type assigned, as shown below:

Restart the Strategy Intelligence Server to reflect the database instance changes.