The input file size is important for sort applications, since it is used for several internal optimizations as well as for dynamic work data set allocation. DFSORT can automatically estimate the file size for disk input data sets and tape data sets managed by DFSMSrmm or a tape management system that uses ICETPEX. However, there are certain situations, which DFSORT reports with message ICE118I, in which DFSORT cannot determine the file size. See "File Size and Dynamic Allocation" in z/OS DFSORT Application Programming Guide for more information on these situations, and what to do about them.