When guaranteed space is specified for a multivolume extended-format sequential data set, the primary space is preallocated on all the volumes. Because data is written to an extended-format data set using data striping (logically consecutive tracks or CIs are written to the data set in a circular manner), secondary space is not allocated until the preallocated primary space on all volumes is used up. For a striped VSAM data set with guaranteed space that has more than 16 volumes, only the first 16 volumes have preallocated space. The secondary amount specified is divided by the number of volumes and rounded up for allocation on each volume.

The amount of preallocated space for VSAM striped data is limited to 16 volumes.