You could look at using APEX_UTIL.SET_PARSING_SCHEMA_FOR_REQUEST to force the parsing schema to the logged-in-user... In Security - Security Attributes, setup the initialization code to use the parsing schema as set ( set it for ALL pages) apex_util.set_parsing_schema_for_request (p_schema => :APP_USER);

This would be run on every page load, so may be some performance implications - make sure you test carefully.

Please keep in mind that the applications *default* parsing schema would still have to be a user which has all the privileges required for the application. You would use the default parsing schema during development in the Builder (Page Designer) when a developer enters SQL or PL/SQL to parse if it's valid, ... When the developer runs the app we would use the database user he specifies during application login. In addition, all privileged application users (database users) would need to be assigned as valid schemas to the workspace, otherwise the above procedure would prevent switching to that database user. The customer can use APEX_INSTANCE_ADMIN.ADD_SCHEMA to add them in a script. Obviously this would also have to be done on the production system.

Note that if you had code that referenced the function "USER", it would still not be the applications user. They would get APEX_PUBLIC_USER or the default parsing user of the app. They would have to use

SYS_CONTEXT('APEX$SESSION', 'APP_USER')

to get the name of the authenticated user.

Thanks to Michael Potter / Patrick Wolf from the APEX team for this info.