To run or execute the Oracle API from the back-end, we need to Initialize the Apps first.

We have API to Initialize the Apps.

To initialize apps using the API, we need to pass few IN parameter values.

The following is the script prepared to initialize apps based on the
Application, User-name and Responsibility name given.

Example:-

DECLARE
   l_appl_id             NUMBER;
   l_appl_name           VARCHAR2 (100) := 'PA';
   l_user_id             NUMBER;
   l_user_name           VARCHAR2 (100) := 'OPERATIONS';
   l_responsibility_id   NUMBER;
   l_resp_name           VARCHAR2 (200)
                                       := 'Projects, Vision Operations (USA)';
BEGIN

-- To get the Application ID of given Application.
   SELECT application_id
     INTO l_appl_id
     FROM fnd_application
    WHERE application_short_name = l_appl_name;

-- To get the User ID information of  given user
   SELECT user_id
     INTO l_user_id
     FROM fnd_user
    WHERE user_name = l_user_name;

-- To get the Resp ID information of the given responsibility.
   SELECT responsibility_id
     INTO l_responsibility_id
     FROM fnd_responsibility_tl
    WHERE responsibility_name = l_resp_name AND application_id = l_appl_id;

--Initialixze the Application to use the API. 
   fnd_global.apps_initialize (l_user_id, l_responsibility_id, l_appl_id);
END;

I Hope the above script would help understanding about the Initializing the Apps API.