DFSORT's Dynamic Storage Adjustment feature (DSA) provides the best use of virtual storage for large sorts. However, if DSA cannot be used because the file size is unknown (as indicated by message ICE118I) or because SIZE=MAX is not in effect, the following guidelines can be used to determine the best amount of virtual storage for the sort.

Table 1 gives guidelines for the recommended minimum virtual storage to use for a sort application based on its data set size. If you do not know the data set size, you can run the application and look at message ICE134I. The table gives a range of virtual storage sizes for each possible data set size. The low end of each range should produce an efficient sort for the given data set size. The high end, in some cases, will enable an even more efficient sort. Using less than the low end will likely produce noticeable degradation while using more than the high end will probably not have a significant impact on performance.

In order to guarantee the most efficient sorting, use the higher end of the range shown. In order to guarantee efficient, but not necessarily optimum sorting, use the lower end. These values are intended for sorting without data space. See Table 1 for storage recommendations for sorting with data space.

Although sort applications can usually run with less virtual storage than the recommended minimum, the recommended amount enables DFSORT to sort most efficiently. Using less than the recommended amount can result in the effects described in Data set size and virtual storage.