Strategy 1>Run below on twice 1 week

Start RMAN
RUN {
   RECOVER COPY OF DATABASE WITH TAG 'diff_update' UNTIL TIME 'SYSDATE - 7';
   BACKUP INCREMENTAL LEVEL 1 FOR RECOVER OF COPY WITH TAG 'diff_update'
       DATABASE;
   }

A- Run Monday to Sat
RMAN>
RUN {
     BACKUP INCREMENTAL LEVEL 1 DATABASE;
   }

B - Sun
RMAN>
RUN {
 BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE;
}

c- END of month 
RMAN>BACKUP DATABASE;  
RMAN> SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';