Oracle Message ORA-18003 - an outline already exists with this signature

ERRORan outline already exists with this signature
CAUSEThe signature generation algorithm generates signatures that are are 16 bytes in length so it is highly unlikely that any 2 signatures will be identical. This message is raised in such a rare case.
ACTIONEither re-issue the statement that led to the outline being created with some whitespace added or force the outline to be created in a different category.