Note the following points when you develop in reserved namespaces:
? System change option
To be able to change objects in namespaces you must set the system change option of your system to modifiable.
Objects in your namespace must be assigned to a package that begins with the namespace ID. Before you begin development work, create packages with namespace prefixes for your projects.
You can also assign local objects and test objects in your namespace to local ($*) and test (T*) packages. Later on you can reassign them to one of the transportable packages in your namespace, if necessary.
You assign objects to a namespace by placing the reserved namespace ID in front of each object name as a prefix.
For more information, see SAP Note 104010 in SAP Support Portal.