Answer
Start from Oracle's own data-dictionary views rather than trying to find a single master list: USER_ views show only objects you personally own (not much if you're not logged in as the application owner), ALL_ views show everything your account is permitted to see (usually the most useful starting point), and DBA_ views show genuinely everything but are restricted to administrators. V$/GV$ views reflect the live running instance (so they reset on restart) rather than the persisted schema. Querying SELECT * FROM DICTIONARY or SELECT * FROM ALL_OBJECTS/ALL_VIEWS is a reasonable jumping-off point for exploring what's there. To see a specific package's actual source code, SELECT DBMS_METADATA.GET_DDL('PACKAGE', '<PACKAGE_NAME>', '<APP_OWNER>') FROM DUAL; (or querying ALL_SOURCE directly) will pull it. If you're also working in the IEE client, enabling System Info at the bottom of the screen shows you which underlying API/view a given screen is currently using, which is a fast way to connect what you see in the UI to where to look in the database.