The question is very general. Let us look into these possibilities:

1. QSAM (sequential) file: You can run it thru SORT utility adding SEQNUM and then sort then sort by SEQNUM in DESC order

2. VSAM: In CICS, you can read backward using READREV;

3. VSAM: I Batch, unload the VSAM file using SORT in DESC order by key value