Oracle Error Message
RMAN-06758: DB_UNIQUE_NAME is not unique in the recovery catalog
Reason for the Error
RMAN could not identify which SPFILE to restore for this target database, because the recovery catalog contained two or more different instances of this database, each with different DB_UNIQUE_NAME values.
Solution
Use the FOR DB_UNIQUE_NAME option to specify the name of the instance whose parameter file you want to restore.