We can change the snap_interval and retention period for the automatic awr snapshot collection, using modify_snapshot_settings function.
The default settings for ‘interval’ and ‘retention’ are 60 minutes and 8 days .

DEFAULT SETTING:

Modify the snapshot setting:( snap_interval 30 min and retention 30 days(60*24*30)

The values for both ‘interval’ and ‘retention’ are expressed in minutes .

Verify the new setting: