Requesting that the system allocate specified tracks to a data set (by using the ABSTR subparameter) is the most stringent request for space. If any of the requested tracks on the volume are occupied, the space cannot be allocated and the job is terminated.
Do not code ABSTR for SMS-managed data sets.
Certain uses of certain devices can require that specific tracks be requested. For example, specific tracks must be allocated to recover a data set that was deleted accidently. In that case you must know on which tracks the data set was.
Specific track requests with user labels
If user labels are specified, LABEL=(,SUL), the user labels are placed on a user label track. This track is the first in the space requested.