You can delete manual backups to free up backup storage.
Deleted manual backups cannot be recovered. Exercise caution when performing this operation.
Procedure
Log in to the management console.
Click in the upper left corner and select a region and a project.
Click Service List. Under Database, click Relational Database Service. The RDS console is displayed.
In the navigation pane on the left, choose Backup Management. On the displayed page, locate the target manual backup to be deleted and choose More > Delete in the Operation column.