Usually rman generates unique name for backup file and save it in 'database' ('dbs') directory, you can specify directory and file name using 'format' clause

run {
allocate channel ch1 type disk;
set maxcorrupt for datafile 1,2,3,4,5,6,7,8,9,10,11 to 0;
backup
incremental level=0
check logical
format='/oracle/oradata/backup/rman/demo/0.%t.%d.%s.%p'
database;
}