Use to upgrade your version to a compatibility mode.
In the 12.1.2 version you started using Global Unique Identifiers (GUIDs) instead of numeric identifiers. The compatibility mode allows you to continue using numeric identifiers.
The compatibility mode allows the customers to migrate the Knowledge Modules, procedures, and any code using odiRef substitution APIs to the new APIs taking GUIDs as arguments. After the migration is completed, you can switch off the repository compatibility mode, in order to take full advantage of the global identifiers. This is a one time operation, once the repository compatibility mode is switched off, there is no turning back as the menu option becomes disabled. From that point on the repository will only function in full GUID mode.
"About Compatibility Mode" in the "Using Compatibility Mode" chapter in Oracle Fusion Middleware Developing Integration Projects with Oracle Data Integrator