only run the SET DBID command in the following specialized circumstances: - You are not connected to a recovery catalog and want to restore the control file or server parameter file (SPFILE) - You are connected to a recovery catalog want to restore the control file, but the database name is not unique in the recovery catalog. - The server parameter (SPFILE) file is lost and you want to restore it. --------- Example: The following shell script uses the DBID to restore the control file because multiple target databases share the same DB_NAME in the catalog. After you have restored the target control file, you can mount the database to restore the rest of the database: ``` rman TARGET / CATALOG rman/rman@catdb <<EOF STARTUP FORCE NOMOUNT; SET DBID = 862893450; # needed to distinguish target from others with same DB_NAME RESTORE CONTROLFILE; # assuming catalog has automatic channel allocation information ALTER DATABASE MOUNT; EOF ``` If you do not set the SET DBID clause, system will report error below; “RMAN-20005: target database name is ambiguous” .