When connecting to an Oracle database, the Sqoop import command requires case-sensitive table names and usernames (typically uppercase). Otherwise the import fails with error message "Attempted to generate class with no columns!"

Prior to the resolution of the issue SQOOP-741, import-all-tables would fail for an Oracle database. See the JIRA for more information.

The import-all-tables command has additional restrictions. See Chapter 8 in the Sqoop User Guide.