Specify the DONOTBLOCK option to exclude a volume from device-level blocking. The SDM uses the device-level blocking function when the primary storage control supports this function. An application might generate significant updates to a primary volume in a single-channel program chain, such as a defragmentation or full-volume restore operation. The device-level blocking algorithm paces the operation to allow the SDM to offload updates efficiently. Consider using the DONOTBLOCK option only for high-performance, sensitive volumes that generate very short updates, such as IMS™ write any data set (WADS) volumes.