On ONtap NAS is there a feature when you can do the 30 days before purging the file
There is no purging as such in ONTAP NAS, this is something your host/client-side applications can deal with it. However, you can use the 'snapshot policy' to define how system creates Snapshot copies of volumes (to protect your data). The policy specifies when to create the Snapshot copies, how many copies to retain, and how to label them. You can also use scheduled snapshots to ensure snapshots are backed up to remote storage for archiving purposes.
This will help.https://kb.netapp.com/Advice_and_Troubleshooting/Data_Storage_Software/ONTAP_OS/Snapshots%3A_including_SnapShot_Issues_and_Solutions
https://docs.netapp.com/us-en/ontap/data-protection/create-snapshot-policy-task.html
Also Snaplock Compliance mode does this.
