ALC: Allocation Group

The fields in this group describe the space allocated to the data or index component defined by the entry.

HI-A-RBA—The highest RBA (plus 1) available within allocated space to store data.

HI-U-RBA—The highest RBA (plus 1) within allocated space that actually contains data. (The RBA of the next completely unused control interval.)

SPACE-PRI—Gives the number of units (indicated under TYPE) of space allocated to the data or index component when the cluster was defined. This amount of space is to be allocated whenever a data component, a key range within the data component, or the data component's associated sequence set (if IMBED is an attribute of the cluster) is extended onto a candidate volume.

SPACE-SEC—Gives the number of units (indicated under TYPE) of space to be allocated whenever a data set (or key range within it) is extended on the same volume.

For nonstriped VSAM data sets, you can specify in the SMS data class parameter whether to use primary or secondary allocation amounts when extending to a new volume. VSAM striped data sets extend by stripe.

The actual amount of space allocated may differ from the amount requested as a result of SMS policies, record formats, system exits, device geometries and other software or hardware features. Additional information on space allocation is provided in z/OS DFSMS Using Data Sets.