The Remove-RDSDBInstance cmdlet lets you remove the existing DB instance. When you remove the DB instance, all the automated snapshot related to the DB instance are also removed and cannot be recovered. All manual snapshots taken by you will be retained. You can initiate the final snapshot of the DB instance as part of the removal operation and the DB instance will have the deleting status until the snapshot is completed. You also have the choice to skip the final snapshot.
To remove a DB instance, you can use the following two variants of the cmdlet.
PS C:\> Remove-RDSDBInstance -DBInstanceIdentifier "copymywebappprd" -FinalDBSnapshotIdentifier "Myfinalsnapshot4webappprd"
Or:
PS C:\> Remove-RDSDBInstance -DBInstanceIdentifier "copymywebappprd" -SkipFinalSnapshot $true
