For Automated backup to work properly, followings are the criteria.
Your DB instance must be in the ACTIVE state for automated backups to occur. Automated backups don't occur while your DB instance is in a state other than ACTIVE, for example STORAGE_FULL.
Automated backups and automated snapshots don't occur while a copy is executing in the same region for the same DB instance.
The first snapshot of a DB instance contains the data for the full DB instance. Subsequent snapshots of the same DB instance are incremental, which means that only the data that has changed after your most recent snapshot is saved.
The following diagram shows how we can configure the automated backup window for a DB instance using the AWS console. To disable the automated backup, set the number of days to zero.
We can also take backups manually by using snapshots. To take a snapshot manually we use the instance action option after selecting the instance as shown below.
We can aslo take manual backup using the CLI with the below command.
