The system will always supply the specified secondary allocation when one is needed unless one of the two events occurs :
? The allocated volume does not have enough space to satisfy the secondary allocation and no other volumes are allocated.
? The needed secondary allocation, if granted, will cause the dataset to exceed 16 extents on the volumes and no other volumes are allocated.
If either of these two conditions arises, the result will be a SB37-04 ABEND failure (normally for a sequential dataset). For a PDS, the ABEND, can also be SE37-04. Please note that a PDS is confined to a single volume, ehile a sequential dataset can extend into a maximum of 59 volumes. The 16-extent-per-volume limit for a dataset is system-supplied and cannot be altered.
The secondary allocation is optional. If omitted, defaults to 0. When no secondary allocation is coded and the primary allocation is exhausted, the result is an SD37-04 ABEND failure.