The DFSORT job below will do what you asked for. I assumed that the records were already sorted as shown in your example. If not, replace OPTION COPY with a SORT statement for 1,3,CH,A.
You'll need z/OS DFSORT V1R5 PTF UQ95214 or DFSORT R14 PTF UQ95213 (Dec, 2004) in order to use DFSORT's RESTART function. Only DFSORT has this function, so if you don't have DFSORT, you won't be able to use it. If you do have DFSORT, but you don't have the Dec, 2004 PTF, ask your System Programmer to install it (it's free). For complete details on all of the new DFSORT and ICETOOL functions available with the Dec, 2004 PTF, see: