Registering Database Instances 
Use
If
database instances are to be managed by the Database Manager GUI, they have to be registered.
Prerequisites
If you want to access a remote database instance with the Database Manager, you have to start the X Server service on the relevant database server (
Status: started).Procedure

You can choose any name as the registered name of the database instance. It only needs to be unique within the Database Manager GUI. Generally speaking it should be the same as the name defined for the database instance during installation. If this has already been assigned you must use a different registered name.
Result
The database instance has been registered and from now on it will appear on the list of registered databases.

To organize your directory of registered database instances, choose File ® New Folder | Delete | Rename.