You can assign system-managed data sets a storage class with the Accessibility attribute set to CONTINUOUS or PREFERRED:

CONTINUOUS

If data sets cannot be allocated on copy-capable volumes, allocation fails.

PREFERRED

SMS attempts to allocate data sets behind a cache-capable 3990 storage control with point-in-time support, IBM® RAMAC Virtual Array device, or ESS. If no space is available, data sets are allocated on a volume that is not supported by point-in-time copy.

STANDARD

The data sets should be allocated on volumes that are not supported by point-in-time copy. If this cannot be done, a data set can be allocated to a volume supported by point-in-time copy.

NOPREF

The data sets should be allocated to volumes whether the volumes support point-in-time copy or not.

If you specify CONTINUOUS or CONTINUOUS PREFERRED to request point-in-time copy, you must then identify which kind of device you want SMS to use: versioning or backup devices.

Versioning Device

creates a "fast" point-in-time version of a data set, which is then available for application testing, reporting, or backup operations. While the version is being made, the data set is unavailable for normal application processing for a minimal period of time. Versioning is done using the SnapShot feature of the RAMAC Virtual Array or the FlashCopy® service of the ESS.

Backup Device

creates a "fast" point-in-time backup copy of a data set. While the backup copy is being made, the data set is unavailable for normal application processing for a minimal period of time. Two methods are supported:

Method 1

Establish a concurrent copy session with the 3990 DASD controller and make the backup copy.

Method 2

Take a point-in-time version, using the virtual concurrent copy service of the IBM ESS or the SnapShot feature of the RAMAC Virtual Array, to create a point-in-time copy and the backup to a specified target device.