If you have an online backup copy, you would use SUPERC to compare the 2 members (tso/ispf 3.13). If the system you use has FileAid, this also has a compare function.
If you are not already fluent with REXX you will need to invest far more time than it is worth to achieve something that is already available. People who know rexx would have trouble with a comprehensive file compare (similar to superc).
Hope this helps,