Details about this incident are available via debug id....

In Oracle Application Express, unexpected exceptions can occasionally occur.  Instead of communicating the technical details to an end user who is running the application, an error message will be issued of the form:

Contact your administrator. Details about this incident are available via debug id "NN".

But what actually happened?  Who is "your administrator"?  And what exactly are you supposed to do with this information?

What happened?

An internal exception occurred - it either wasn't properly handled by the application's error handler (or there was no handler in place), or an unforeseen exception occurred in the Application Express engine itself, which wasn't properly caught by the error handler of APEX.  If you're logged into the development environment as a developer and running the application, you should be able to see the full error stack and more details of what actually occurred.  But if you're a mere end-user of the application, you are shielded from those details - not only would the details be mystifying to an end user, but it could also be viewed as a security risk, to show the details.

Who is "your administrator"?

• A developer of this application, who has access to SQL Commands in the APEX workspace?
• A developer who can connect directly to the database where this error occurred, connecting as the database user associated with the workspace (commonly referred as the "workspace schema").
• A database user who has been granted the APEX_ADMINISTRATOR_ROLE (or, beginning in APEX 5.1, also the APEX_ADMINISTRATOR_READ_ROLE).
• Someone who can connect as SYS or SYSTEM to your database.

What can you do with this information?

The full details of the incident and the error stack at the time of the exception are written to the Debug Messages tables in the Application Express schema.  To view these details, you simply need to query the view APEX_DEBUG_MESSAGES:

select *
  from apex_debug_messages
 where page_view_id = NN
 order by message_timestamp asc;

This information is also accessible from the development environment of Application Express.

• A developer can select their application in App Builder, and then navigate to Utilities -> Debug Messages.
• A workspace administrator can navigate to Workspace Administration -> Monitor Activity -> Page Views By View.  You can then filter the output by the Debug ID column.