Oracle Error Message
RMAN-05537: DUPLICATE without TARGET connection when auxiliary instance is started with spfile cannot use SPFILE clause
Reason for the Error
A DUPLICATE was attempted when the auxiliary database was started with a server parameter file and the SPFILE sub-clause was specified. RMAN cannot restore the server parameter file if the auxiliary database is already started with a server parameter file.
Solution
Start the auxiliary database with a client parameter file or do not specify SPFILE sub-clause and retry.