Oracle does not support attaching databases like SQL Server does. The closest thing Oracle has is the Transportable Tablespace (TTS). To attach a tablespace with TTS, you would need the metadata dump file, the tablespace's datafiles, and the Oracle import utility.
The ORA-3121 error is "no interface driver connected - function not performed". Without knowing exactly what you were doing, and how you were doing it, I cannot guess as to why this error was received other than to say that attaching a database is not an Oracle-supported operation.
This was first published in June 2005