The general rules discussed for striped extended format data sets apply to striped VSAM data sets. When the system allocates space for a striped extended-format data set, the system divides the primary amount among the volumes. If the primary amount is not divided evenly, the system rounds up the amount. For extended-format data sets, when the primary space on any volume is full, the system allocates space on that volume. The amount is the secondary amount divided by the number of stripes. If the secondary amount does not divide evenly, the system rounds up the amount. The system might have to perform additional rounding of space for each stripe if one or more extended address volumes have been selected. This situation might happen when cylinder-managed space has been selected which might cause the requested space amount of that stripe to be rounded to the next multi-cylinder unit. The remaining stripes space amount is adjusted to match to ensure all stripes contain the same amount of space. This only occurs after attempts by the system to allocate the exact amount for each stripe does not succeed.

Some additional considerations apply to the control area (CA) for VSAM. All allocations must be rounded to a CA boundary. The number of stripes influences the size of the control area, resulting in some differences in allocation quantity required to meet the stripe count and CA requirements. The following topic on CA size considerations discusses this in more detail.

All data set extends are as described for striped data set extends. Basically, the system divides the secondary amount by the stripe count and allocates the result to each stripe. This occurs in all cases, including a data set with the guaranteed space attribute from the associated storage class (SC), as well as extending to a new layer.

Restriction: Volume High Used RBA statistics do not apply for multistriped VSAM data sets. The high-use RBA is kept on the volume for the first stripe because the value is the same for all stripes.