Oracle RMAN backup for RAC Policy Managed DB

Hi 
I had 5 Node RAC with Policy managed database, where multiple PDB running based on importance and I had to create the cron shell script to take the backup. Most of Container DB are on two nodes only. As Policy managed database changed their Instance Name on each failover and they can also go to any other node based on serverpool and Database configuration. So can some one share as what can be best way to put cron running from all nodes and making sure only one backup of a particular database is running on daily basis. Appreciate any help in the logic
TxSanjay

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