You need to provide a lot more information before anyone on this board can help you and maybe not even then.
Which sort product are you using (DFSORT, Syncsort, CA-SORT)? What do your JCL and control statements look like? Are you calling SORT directly or from a program? Do you have exits? Etc, etc. But even with all that, it's likely nobody will be able to help you debug the problem without a dump.