I had a page that wouldn't run - I just kept getting errors like:
"The requested URL /pls/otn/f was not found on this server."
Our DBA searched the Apache logs and found this:
ORA-20001: Package variable g_security_group_id must be set.
ORA-06512: at "FLOWS_030000.F", line 279
ORA-06512: at line 7
By deconstructing the page bit by bit I eventually found the cause: an item with a source type of "PL/SQL Expression or Function" and a source value that was invalid (it called a function that didn't exist). Once the page was cut down sufficiently an appropriate error message was displayed.
I have duplicated the problem page here:
In this case it is an item P220_LTL_REFERENCE with a source type of "PL/SQL Expression or Function" and a source of "no_such_function". If I change the source type to "Static" or the source to a valid expression the page loads fine.