Improving Performance with the Parallel Access Volume Option

The Enterprise Storage Server® (ESS) allows for concurrent data transfer operations to or from the same volume on the same system. A volume used in this way is called a Parallel Access Volume (PAV). With ESS, you can define alias device numbers to represent one physical device which allows for multiple I/O operations to be started at one time which improves performance.

The Storage Class option for Parallel Access Volumes may be used to influence volume selection in such a way that data sets that require high performance may be directed towards volumes that are being used as Parallel Access Volumes. The DFSMS volume selection process puts eligible volumes into the primary, secondary, or tertiary category. For more information about the volume selection process, see Selecting Volumes with SMS.

The DFSMS PAV capability option includes the following settings based on the volume selection categories:

Required: Only volumes with the PAV feature enabled are selected.
Preferred: Volumes with the PAV feature enabled are eligible to be primary volumes. Volumes without the PAV feature enabled are only eligible to be secondary volumes.
Standard: Volumes without the PAV feature enabled are preferred over volumes with the PAV feature enabled and are eligible to be primary volumes. Volumes with the PAV feature enabled are only eligible to be secondary volumes.
Nopreference: Whether the PAV feature is enabled or not for a volume is ignored and has no effect on the volume selection process. This is the default value for this option.