Script within RMAN Catalog

To Create a Global Script
CREATE GLOBAL SCRIPT backup_db
COMMENT "back up any database from the recovery catalog, with logs"
{ BACKUP DATABASE;}

To Replace a Global Script
REPLACE GLOBAL SCRIPT backup_db { BACKUP DATABASE PLUS ARCHIVELOG; }

To replace a Script
REPLACE SCRIPT backup_db { BACKUP DATABASE PLUS ARCHIVELOG; }

To delete a script 
DELETE SCRIPT backup_db;

To print a Global Script
PRINT GLOBAL SCRIPT backup_db;

To run a Script within catalog 
RMAN> RUN { EXECUTE GLOBAL SCRIPT global_backup_db; }
e.g.
run {backup_all_archivelog_delete_imput)}

SCRIPT WITH VARIABLE 
REPLACE SCRIPT backup_df { BACKUP DATAFILE &1 TAG &2.1 FORMAT '/backup_rman/&3_%U'; }
1=1
2=df1_backup
3=df1
To run with variable 
RUN { EXECUTE SCRIPT backup_df USING 3 test_backup df3; }

RUN { EXECUTE SCRIPT backup_df USING 1 backup_DF_1 df1; }