One or more storage units that are defined from the disk units or disk-unit subsystems that make up addressable disk storage. Disk pools (which are also known as auxiliary storage pools ) provide a means of placing certain objects on specific disk units to limit the impact of disk-media failures and to reduce recovery time. A basic disk pool contains both objects and the libraries or directories that contain the objects. Attributes such as authorization, ownership, and spooled file attributes are stored in the system disk pool (also known as the system ASP).