by Robert Sample » Thu Sep 02, 2010 8:12 pm
Space calculation estimates are easy -- take the number of blocks times the block size to get the total bytes used. If the data set is allocated on more than 1 volume, add up the number of blocks on each volume to get total blocks, then multiply.
If a data set requires more space than a single volume allows then you have no choice but use multiple volumes. This is quite common for tapes, and can occur for disk data sets -- a 3390 mod 3, for example, can hold about 2.8 GB of data; if your data set has more than that you have no choice but allocate additional volumes for it.