The Oracle connection is successful, and the first leg of DB processing completes, it's only when trying to complete the second leg of processing that this error occurs.
Steps:
1. File A is read from, and aggregated into File B
2. File B is read from, and aggregated into File C
The remaining steps all read from File C and perform other functions into various other files.
It's during Step 2 that the error occurs, after File B has been populated (verified through Oracle SQL Developer), when trying to read from File B and aggregate into File C.